DUSP4 modulates RIG-I- and STING-mediated IRF3-type I IFN response

Detection of cytosolic nucleic acids by pattern recognition receptors, including STING and RIG-I, leads to the activation of multiple signalling pathways that culminate in the production of type I interferons (IFNs) which are vital for host survival during virus infection. In addition to protective immune modulatory functions, type I IFNs are also associated with autoimmune diseases. Hence, it is important to elucidate the mechanisms that govern their expression. In this study, we identified a critical regulatory function of the DUSP4 phosphatase in innate immune signalling. We found that DUSP4 regulates the activation of TBK1 and ERK1/2 in a signalling complex containing DUSP4, TBK1, ERK1/2 and IRF3 to regulate the production of type I IFNs. Mice deficient in DUSP4 were more resistant to infections by both RNA and DNA viruses but more susceptible to malaria parasites. Therefore, our study establishes DUSP4 as a regulator of nucleic acid sensor signalling and sheds light on an important facet of the type I IFN regulatory system.

Severity of SARS-CoV-2 Omicron XBB subvariants in Singapore

Several XBB subvariants such as XBB.1.5, XBB.1.9, XBB.1.16 and XBB.2.3 co-circulate in Singapore. Despite the different viral properties of XBB.1.16 as compared to other XBB subvariants, comparison on their severity is limited. In this study, we investigate the outcomes of hospitalisation and severe COVID-19 infection in individuals infected with different XBB subvariants, adjusted for potential confounders such as age and vaccination history. Overall, our preliminary analysis showed that the risk of severe outcomes when infected with XBB.1.16 is higher than that of XBB.1.5 or XBB.1.9 but there is no difference in the risk of hospitalisation across different XBB subvariants.

Erratum to "Impact of delta variant and vaccination on SARS-CoV-2 secondary attack rate among household close contacts" [The Lancet Regional Health - Western Pacific 17 (2021) 100299]

[This corrects the article DOI: 10.1016/j.lanwpc.2021.100299.].

Conserved longitudinal alterations of anti-S-protein IgG subclasses in disease progression in initial ancestral Wuhan and vaccine breakthrough Delta infections

INTRODUCTION

COVID-19 has a wide disease spectrum ranging from asymptomatic to severe. While humoral immune responses are critical in preventing infection, the immune mechanisms leading to severe disease, and the identification of biomarkers of disease progression and/or resolution of the infection remains to be determined.

METHODS

Plasma samples were obtained from infections during the initial wave of ancestral wildtype SARS-CoV-2 and from vaccine breakthrough infections during the wave of Delta variant, up to six months post infection. The spike-specific antibody profiles were compared across different severity groups and timepoints.

RESULTS

We found an association between spike-specific IgM, IgA and IgG and disease severity in unvaccinated infected individuals. In addition to strong IgG1 and IgG3 response, patients with severe disease develop a robust IgG2 and IgG4 response. A comparison of the ratio of IgG1 and IgG3 to IgG2 and IgG4 showed that disease progression is associated with a smaller ratio in both the initial wave of WT and the vaccine breakthrough Delta infections. Time-course analysis revealed that smaller (IgG1 and IgG3)/(IgG2 and IgG4) ratio is associated with disease progression, while the reverse associates with clinical recovery.

DISCUSSION

While each IgG subclass is associated with disease severity, the balance within the four IgG subclasses may affect disease outcome. Acute disease progression or infection resolution is associated with a specific immunological phenotype that is conserved in both the initial wave of WT and the vaccine breakthrough Delta infections.

Effect of a Popular Web Drama Video Series on HIV and Other Sexually Transmitted Infection Testing Among Gay, Bisexual, and Other Men Who Have Sex With Men in Singapore: Community-Based, Pragmatic, Randomized Controlled Trial

Background

Gay, bisexual, and other men who have sex with men (GBMSM) are at disproportionately higher risk of acquiring HIV and other sexually transmitted infections (STI). While HIV/STI testing rates among GBMSM are increasing worldwide, they remain suboptimal in a variety of settings. While many studies have attempted to evaluate the efficacy of a variety of community-based campaigns, including peer and reminder-based interventions on HIV/STI testing, however few have attempted to do so for a web drama series.

Objective

This study evaluates the effectiveness of a popular web drama video series developed by a community-based organization in Singapore for GBMSM on HIV and other STI testing behaviors.

Methods

The study is a pragmatic, randomized controlled trial to evaluate a popular web drama video series developed by a community-based organization in Singapore for GBMSM. A total of 300 HIV-negative, GBMSM men in Singapore aged 18 to 29 years old were recruited and block-randomized into the intervention (n=150) and control arms (n=150). Primary outcomes included changes in self-reported intention to test for, actual testing for, and regularity of testing for HIV, syphilis, chlamydia or gonorrhea, while secondary outcomes include changes in a variety of other knowledge-based and psychosocial measures at the end of the study period.

Results

Overall, 83.3% (125/150) of participants in the intervention arm completed the proof of completion survey, compared to 88.7% (133/150) in the control arm. We found improvements in self-reporting as a regular (at least yearly) tester for HIV (15.9% difference, 95% CI, 3.2% to 28.6%; P=.02), as well as chlamydia or gonorrhea (15.5% difference, 95% CI, 4.2% to 26.9%; P=.009), indicating that the intervention had positively impacted these outcomes compared to the control condition. We also found improvements in participants’ intentions to test for HIV (16.6% difference, 95% CI, 4.3% to 28.9%; P=.009), syphilis (14.8% difference, 95% CI, 3.2% to 26.4%; P=.01), as well as chlamydia or gonorrhea (15.4% difference, 95% CI, 4.2% to 26.6%; P=.008), in the next 3 months, indicating that the intervention was effective in positively impacting intention for HIV and other STI testing among participants.

Conclusions

There are clear benefits for promoting intentions to test regularly and prospectively on a broad scale through this intervention. This intervention also has potential to reach GBMSM who may not have access to conventional HIV and other STI prevention messaging, which have typically been implemented at sex-on-premises venues, bars, clubs, and in sexual health settings frequented by GBMSM. When coupled with community or population-wide structural interventions, the overall impact on testing will likely be significant.

Trial Registration

ClinicalTrials.gov NCT04021953; https://clinicaltrials.gov/ct2/show/NCT04021953

International Registered Report Identifier (IRRID)

RR2-10.1136/bmjopen-2019-033855

Prevalence of measles antibodies among migrant workers in Singapore: a serological study to identify susceptible population subgroups

Background

In 2019, two clusters of measles cases were reported in migrant worker dormitories in Singapore. We conducted a seroprevalence study to measure the level of susceptibility to measles among migrant workers in Singapore.

Methods

Our study involved residual sera of migrant workers from seven Asian countries (Bangladesh, China, India, Indonesia, Malaysia, Myanmar and the Philippines) who had participated in a survey between 2016 and 2019. Immunoglobulin G (IgG) antibody levels were first measured using a commercial enzyme-linked immunosorbent assay (ELISA) test kit. Those with equivocal or negative IgG results were further evaluated using plaque reduction neutralization test (PRNT).

Results

A total of 2234 migrant workers aged 20–49 years were included in the study. The overall prevalence of measles IgG antibodies among migrant workers from the seven Asian countries was 90.5% (95% confidence interval 89.2–91.6%). The country-specific seroprevalence ranged from 80.3 to 94.0%. The seroprevalence was significantly higher among migrant workers born in 1965–1989 than those born in 1990–1999 (95.3% vs. 86.6%, p < 0.0005), whereas there was no significant difference by gender (90.8% in men vs. 89.9% in women, p = 0.508). 195 out of 213 samples with equivocal or negative ELISA results were tested positive using PRNT.

Conclusion

The IgG seroprevalence in migrant workers was below the herd immunity threshold of 95% for measles. Sporadic outbreaks may occur in susceptible individuals due to high transmissibility of measles virus. Seroprevalence surveys can help identify susceptible subgroups for vaccination.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07066-2.

Seroprevalence of IgG antibodies against diphtheria antitoxin among migrant workers in Singapore, 2016-2019

Background

Since the last local case of diphtheria in 1992, there had not been any case in Singapore until an autochthonous case was reported in 2017. This fatal diphtheria case of a migrant worker raised concerns about the potential re-emergence of locally transmitted toxigenic diphtheria in Singapore. We conducted a seroprevalence study to assess the immunity levels to diphtheria among migrant workers in Singapore.

Methods

Residual sera from migrant workers who hailed from Bangladesh, China, India, Indonesia, Malaysia, Myanmar and the Philippines were tested for anti-diphtheria toxoid immunoglobulin G (IgG) antibodies. These migrant workers previously participated in a survey between 2016 and 2019 and had provided blood samples as part of the survey procedure.

Results

A total of 2176 migrant workers were included in the study. Their overall mean age was 27.1 years (standard deviation 5.0), range was 20–43 years. The proportion having at least basic protection against diphtheria (antitoxin titres ≥ 0.01 IU/ml) ranged from 77.9% (95% confidence interval [CI] 72.8 – 82.3%) among migrant workers from Bangladesh to 96.7% (95% CI 92.5 – 98.6%) in those hailing from Malaysia. The proportion showing full protection (antitoxin titres ≥ 0.10 IU/ml) ranged from 10.1% (95% CI 6.5 – 15.4%) in Chinese workers to 23.0% (95% CI 17.1 – 30.3%) in Malaysian workers. There were no significant differences in the proportion with at least basic protection across birth cohorts, except for those from Bangladesh where the seroprevalence was significantly lower in younger migrant workers born after 1989.

Conclusions

The proportions having at least basic protection against diphtheria in migrant workers from five out of seven Asian countries (India, Indonesia, Malaysia, Myanmar and the Philippines) were higher than 85%, the threshold for diphtheria herd immunity. Seroprevalence surveys should be conducted periodically to assess the level of immunity against diphtheria and other vaccine preventable diseases in migrant worker population, so that appropriate interventions such as booster vaccination can be implemented proactively to prevent sporadic outbreaks.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-12528-y.

Impact of Delta Variant and Vaccination on SARS-CoV-2 Secondary Attack Rate Among Household Close Contacts

BACKGROUND

Impact of the Delta variant and vaccination on SARS-CoV-2 transmission remains unclear. In Singapore, quarantine of all close contacts, including entry and exit PCR testing, provided the opportunity to determine risk of infection by the Delta variant compared to other variants, vaccine efficacy against SARS-CoV-2 acquisition, symptomatic or severe COVID-19, and risk factors associated with SARS-CoV-2 acquisition and symptomatic disease.

METHODS

This retrospective cohort study included all close contacts between September 1, 2020 and May 31, 2021. Regardless of symptoms, all were quarantined for 14 days with entry and exit PCR testing. Household contacts were defined as individuals who shared a residence with a Covid-19 index case. Secondary attack rates among household close contacts of Delta variant-infected indexes and other variant-infected indexes were derived from prevalence of diagnosed cases among contacts. Relative risk ratios and bootstrapping at the cluster level was used to determine risk of infection by the Delta variant compared to other variants and vaccine efficacy against SARS-CoV-2 acquisition, symptomatic or severe COVID-19. Logistic regression using generalized estimating equations was used to determine risk factors associated with SARS-CoV-2 acquisition and symptomatic disease.

FINDINGS

Of 1024 household contacts linked to 301 PCR-confirmed index cases, 753 (73.5%) were linked to Delta-infected indexes and 248 (24.2%) were exposed to indexes with other variants. Household secondary attack rate among unvaccinated Delta-exposed contacts was 25.8% (95% boostrap confidence interval [BCI] 20.6-31.5%) compared with 12.9% (95%BCI 7.0-20.0%) among other variant-exposed contacts. Unvaccinated Delta-exposed contacts were more likely to be infected than those exposed to other variants (Relative risk 2.01, 95%CI 1.24-3.84). Among Delta-exposed contacts, complete vaccination had a vaccine effectiveness of 56.4% (95%BCI 32.6-75.8%) against acquisition, 64.1% (95%BCI 37.8-85.4%) against symptomatic disease and 100% against severe disease. Among Delta-exposed contacts, vaccination status (adjusted odds ratio [aOR] 0.33, 95% robust confidence interval [RCI] 0.17-0.63) and older age of the index (aOR 1.20 per decade, 95%RCI 1.03-1.39) was associated with increased risk of SARS-CoV-2 acquisition by the contact. Vaccination status of the index was not associated with a statistically-significant difference for contact SARS-CoV-2 acquisition (aOR 0.73, 95%RCI 0.38-1.40).

INTERPRETATION

Increased risk of SARS-CoV-2 Delta acquisition compared with other variants was reduced with vaccination. Close-contacts of vaccinated Delta-infected indexes did not have statistically significant reduced risk of acquisition compared with unvaccinated Delta-infected indexes.

Accuracy of a rapid multiplex PCR plus a chromogenic phenotypic test algorithm for detection of ESBL and carbapenemase-producing Gram-negative bacilli in positive blood culture bottles

We studied the performance of an algorithm combining multiplex-PCR with phenotypic detection of ESBLs and carbapenemases directly from positive blood culture bottles in patients with Gram-negative bacteremia and found good concordance with routine cultures. Such an algorithm may be a tool to improve time-to-optimal therapy in patients with Gram-negative bacteremia.

Rapid measurement of SARS-CoV-2 spike T cells in whole blood from vaccinated and naturally infected individuals

Defining the correlates of protection necessary to manage the COVID-19 pandemic requires the analysis of both antibody and T cell parameters, but the complexity of traditional tests limits virus-specific T cell measurements. We tested the sensitivity and performance of a simple and rapid SARS-CoV-2 spike protein-specific T cell test based on the stimulation of whole blood with peptides covering the SARS-CoV-2 spike protein, followed by cytokine (IFN-γ, IL-2) measurement in different cohorts including BNT162b2-vaccinated individuals (n = 112), convalescent asymptomatic and symptomatic COVID-19 patients (n = 130), and SARS-CoV-1-convalescent individuals (n = 12). The sensitivity of this rapid test is comparable to that of traditional methods of T cell analysis (ELISPOT, activation-induced marker). Using this test, we observed a similar mean magnitude of T cell responses between the vaccinees and SARS-CoV-2 convalescents 3 months after vaccination or virus priming. However, a wide heterogeneity of the magnitude of spike-specific T cell responses characterized the individual responses, irrespective of the time of analysis. The magnitude of these spike-specific T cell responses cannot be predicted from the neutralizing antibody levels. Hence, both humoral and cellular spike-specific immunity should be tested after vaccination to define the correlates of protection necessary to evaluate current vaccine strategies.

HIV Pre-Exposure Prophylaxis, Condoms, or Both? Insights on Risk Compensation Through a Discrete Choice Experiment and Latent Class Analysis Among Men Who Have Sex With Men

OBJECTIVES

We considered how decision making around human immunodeficiency virus (HIV) pre-exposure prophylaxis (PrEP) among gay, bisexual, and other men who have sex with men (GBMSM) is made in the context of one's perceived risk of HIV acquisition and the availability of condoms.

METHODS

We recruited 648 GBMSM aged 18 years old and residing in Singapore through Grindr. Participants were given information on PrEP and participated in a discrete choice experiment requiring them to choose between 2 baskets of PrEP attributes and compare the chosen "PrEP only" option to default options of "condoms only" or "PrEP with condoms." Generalized multinomial logit model was used to examine the scaling effect and preference heterogeneity. Latent class analysis was conducted to examine preference heterogeneity in the sample.

RESULTS

Latent class analysis revealed 3 classes of GBMSM: PrEP conservatives (53.9%), moderates (31.1%), and liberals (14.9%). PrEP conservatives were more likely to report greater utility when using condoms only compared with PrEP only, as well as PrEP with condoms, compared with PrEP only, and more likely to report the lowest utility for PrEP as perceived HIV risk increased. PrEP liberals were more likely to report greatest utilities for PrEP only compared with condoms only, as well as PrEP only compared with PrEP with condoms. The utility for PrEP was not affected by perceived risk of HIV or sexually transmitted infections when risks were low.

CONCLUSION

This study provides some evidence for risk compensation among a class of GBMSM who already perceived themselves to be good candidates for PrEP before the discrete choice experiment.

Sensitive detection of total anti-Spike antibodies and isotype switching in asymptomatic and symptomatic individuals with COVID-19

Early detection of infection is crucial to limit the spread of coronavirus disease 2019 (COVID-19). Here we develop a flow cytometry-based assay to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein antibodies in individuals with COVID-19. The assay detects specific immunoglobulin M (IgM), IgA, and IgG in individuals with COVID-19 and also acquisition of all IgG subclasses, with IgG1 being the most dominant. The antibody response is significantly higher at a later stage of infection. Furthermore, asymptomatic individuals with COVID-19 also develop specific IgM, IgA, and IgG, with IgG1 being the most dominant subclass. Although the antibody levels are lower in asymptomatic infection, the assay is highly sensitive and detects 97% of asymptomatic infections. These findings demonstrate that the assay can be used for serological analysis of symptomatic and asymptomatic infections, which may otherwise remain undetected.

Flow cytometry assay detects specific antibodies in symptomatic individuals with COVID-19

Asymptomatic individuals with COVID-19 also develop specific antibodies

IgG1 is the dominant IgG subclass in symptomatic and asymptomatic individuals

The assay is highly sensitive and detects 97% of asymptomatic infections

Perceptions of an HIV self-testing intervention and its potential role in addressing the barriers to HIV testing among at-risk heterosexual men: a qualitative analysis

Objectives

Voluntary HIV testing rates are still low in several Asian countries including Singapore. HIV self-testing (HIVST) has the potential to increase testing, leading to earlier diagnosis and better prognosis. However, the views of at-risk individuals, especially heterosexual men (HSM), who are not coming forward for testing are still poorly understood. In this study, we examined the barriers and facilitators to and delivery preferences for HIVST in order to implement an effective intervention in Singapore.

Methods

From May 2017 to June 2018, 48 in-depth interviews were conducted with HSM aged 21–66 years and at risk of HIV infection. Participants were purposively sampled based on ethnicity, age and testing behaviour. Recruitment was done mainly at brothels and entertainment establishments in Singapore. Participants gave their views on HIV testing, factors affecting HIVST use and their preferred HIVST service delivery model.

Results

Most participants preferred HIVST over conventional testing for its convenience, privacy, anonymity and autonomy, but older men still preferred conventional testing. Low self-perceived risk, low awareness and self-efficacy for HIVST, and non-comprehensive test for other STIs were reported as barriers to HIVST. There were mixed opinions on kit preference. A blood-based kit was favoured for higher accuracy, while the oral-fluid-based kit was favoured for ease of use. Participants wanted a human touch for post-test counselling and linkage to care only if they self-tested positive. Traditional media, internet and social media, and venue-based outreach were potential advertising platforms mentioned.

Conclusions

A locally acceptable and feasible HIVST intervention must address the barriers and facilitators of using HIVST in order to improve HIV testing rates among this at-risk population who might otherwise delay or fail to present for testing.

Effectiveness of Containment Measures Against COVID-19 in Singapore: Implications for Other National Containment Efforts

BACKGROUND

We hypothesize that comprehensive surveillance of COVID-19 in Singapore has facilitated early case detection and prompt contact tracing and, with community-based measures, contained spread. We assessed the effectiveness of containment measures by estimating transmissibility (effective reproduction number, (Equation is included in full-text article.)) over the course of the outbreak.

METHODS

We used a Bayesian data augmentation framework to allocate infectors to infectees with no known infectors and determine serial interval distribution parameters via Markov chain Monte Carlo sampling. We fitted a smoothing spline to the number of secondary cases generated by each infector by respective onset dates to estimate (Equation is included in full-text article.)and evaluated increase in mean number of secondary cases per individual for each day's delay in starting isolation or quarantine.

RESULTS

As of April 1, 2020, 1000 COVID-19 cases were reported in Singapore. We estimated a mean serial interval of 4.6 days [95% credible interval (CI) = 4.2, 5.1] with a SD of 3.5 days (95% CI = 3.1, 4.0). The posterior mean (Equation is included in full-text article.)was below one for most of the time, peaking at 1.1 (95% CI = 1.0, 1.3) on week 9 of 2020 due to a spreading event in one of the clusters. Eight hundred twenty-seven (82.7%) of cases infected less than one person on average. Over an interval of 7 days, the incremental mean number of cases generated per individual for each day's delay in starting isolation or quarantine was 0.03 cases (95% CI = 0.02, 0.05).

CONCLUSIONS

We estimate that robust surveillance, active case detection, prompt contact tracing, and quarantine of close contacts kept (Equation is included in full-text article.)below one.

Potential interactions between the pathways to diagnosis of HIV and other STIs and HIV self-testing: insights from a qualitative study of gay, bisexual and other men who have sex with men in Singapore

Objectives

This study draws on qualitative insights on the barriers and facilitators to HIV testing, as well as perceptions of HIV self-testing (HIVST), to propose a framework to understand not only the benefits but also potential knock-on implications of introducing HIVST in the context of other STI testing.

Methods

We conducted semistructured, in-depth interviews with 30 gay, bisexual and other men who have sex with men aged 18 and 39 years old in Singapore. Interview topics included barriers and facilitators to HIV and other STI testing, as well as perceptions of HIVST. Interviews were audio-recorded, transcribed, coded and analysed using thematic analysis.

Results

For HIV testing, participants cited the perceived risk of acquiring, susceptibility to and symptoms of HIV as internal motivators, while social influence and accessibility of HIV testing services were external motivators. For STI testing, perceived symptoms and partner notification of STI were reported as internal and external motivators, respectively. Availability of bundle tests, starting a new relationship and instances of mandatory testing motivated both simultaneous HIV and other STI testing. The fear of a positive diagnosis and lack of confidentiality were cited as internal and external barriers to HIV testing, respectively, while low perceived severity of other STI and the cost of STI tests were cited as internal and external barriers to other STI testing, respectively. We identified pathways to HIV and other STI testing and discussed how the introduction of HIVST may reduce opportunities for other STI testing.

Conclusions

The findings of this study suggest that introducing HIVST might weaken linkages to other STI testing if alternative strategies of promoting other STI testing are not simultaneously implemented. We recommend that future interventions address both the risks of HIV and other STI simultaneously, and that structural interventions promoting HIV and other STI preventions be balanced accordingly.

Two linear epitopes on the SARS-CoV-2 spike protein that elicit neutralising antibodies in COVID-19 patients

Given the ongoing SARS-CoV-2 pandemic, identification of immunogenic targets against the coronavirus spike glycoprotein will provide crucial advances towards the development of sensitive diagnostic tools and potential vaccine candidate targets. In this study, using pools of overlapping linear B-cell peptides, we report two IgG immunodominant regions on SARS-CoV-2 spike glycoprotein that are recognised by sera from COVID-19 convalescent patients. Notably, one is specific to SARS-CoV-2, which is located in close proximity to the receptor binding domain. The other region, which is localised at the fusion peptide, could potentially function as a pan-SARS target. Functionally, antibody depletion assays demonstrate that antibodies targeting these immunodominant regions significantly alter virus neutralisation capacities. Taken together, identification and validation of these neutralising B-cell epitopes will provide insights towards the design of diagnostics and vaccine candidates against this high priority coronavirus.

Epidemiologic Features and Clinical Course of Patients Infected With SARS-CoV-2 in Singapore

IMPORTANCE

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, China, in December 2019 and has spread globally with sustained human-to-human transmission outside China.

OBJECTIVE

To report the initial experience in Singapore with the epidemiologic investigation of this outbreak, clinical features, and management.

DESIGN, SETTING, AND PARTICIPANTS

Descriptive case series of the first 18 patients diagnosed with polymerase chain reaction (PCR)-confirmed SARS-CoV-2 infection at 4 hospitals in Singapore from January 23 to February 3, 2020; final follow-up date was February 25, 2020.

EXPOSURES

Confirmed SARS-CoV-2 infection.

MAIN OUTCOMES AND MEASURES

Clinical, laboratory, and radiologic data were collected, including PCR cycle threshold values from nasopharyngeal swabs and viral shedding in blood, urine, and stool. Clinical course was summarized, including requirement for supplemental oxygen and intensive care and use of empirical treatment with lopinavir-ritonavir.

RESULTS

Among the 18 hospitalized patients with PCR-confirmed SARS-CoV-2 infection (median age, 47 years; 9 [50%] women), clinical presentation was an upper respiratory tract infection in 12 (67%), and viral shedding from the nasopharynx was prolonged for 7 days or longer among 15 (83%). Six individuals (33%) required supplemental oxygen; of these, 2 required intensive care. There were no deaths. Virus was detectable in the stool (4/8 [50%]) and blood (1/12 [8%]) by PCR but not in urine. Five individuals requiring supplemental oxygen were treated with lopinavir-ritonavir. For 3 of the 5 patients, fever resolved and supplemental oxygen requirement was reduced within 3 days, whereas 2 deteriorated with progressive respiratory failure. Four of the 5 patients treated with lopinavir-ritonavir developed nausea, vomiting, and/or diarrhea, and 3 developed abnormal liver function test results.

CONCLUSIONS AND RELEVANCE

Among the first 18 patients diagnosed with SARS-CoV-2 infection in Singapore, clinical presentation was frequently a mild respiratory tract infection. Some patients required supplemental oxygen and had variable clinical outcomes following treatment with an antiretroviral agent.

Effect of a web drama video series on HIV and other sexually transmitted infection testing among gay, bisexual and queer men: study protocol for a community-based, pragmatic randomised controlled trial in Singapore: the People Like Us (PLU) Evaluation Study

INTRODUCTION

Gay, bisexual and queer (GBQ) men are at disproportionately higher risk of acquiring HIV and other sexually transmitted infections (STI). While HIV/STI testing rates among GBQ men are increasing worldwide, they remain suboptimal in a variety of settings.

METHODS AND ANALYSIS

The study is a pragmatic randomised controlled trial designed to evaluate an online video series developed by a community-based organisation in Singapore for GBQ men. A total of 300 HIV-negative GBQ men in Singapore aged 18-29 years old will be recruited for this study. Participants will subsequently be randomised into the intervention arm (n=150) and the control arm (n=150). The intervention arm (n=150) will be assigned the intervention along with sexual health information via a pamphlet, while the control group (n=150) will be assigned only the sexual health information via a pamphlet. Participants should also not have watched the video prior to their participation in this study, which will be ascertained through a questionnaire. Primary outcomes for this evaluation are changes in self-reported intention to test for, actual testing for and regularity of testing for HIV, syphilis, chlamydia and gonorrhoea at the 3 and 6 months after intervention. Secondary outcomes include changes in self-reported risk perception for HIV and other STIs, knowledge of HIV, knowledge of risks associated with acquiring STIs, knowledge of HIV pre-exposure prophylaxis, consistent condom use for anal sex with casual partners, incidence of STIs, connectedness to the lesbian, gay, bisexual and transgender community, self-concealment of sexual orientation, perceived homophobia, internalised homophobia, HIV testing self-efficacy and HIV testing social norms.

ETHICS AND DISSEMINATION

The study has been approved by the National University of Singapore Institutional Review Board (S-19-059) and registered at ClinicalTrials.gov. The results will be published in peer-reviewed academic journals and disseminated to community-based organisations and policymakers.

TRIAL REGISTRATION NUMBER

NCT04021953.

Developing a Typology of HIV/STI Testing Patterns Among Gay, Bisexual, and Queer Men: A Framework to Guide Interventions

Although factors associated with HIV/sexually transmitted infection (STI) testing among gay, bisexual, and queer (GBQ) men are well-established in the literature, few studies have attempted to delineate the processes underlying different patterns of testing. We conducted a qualitative study involving 35 semistructured interviews with a purposive sample of GBQ men in Singapore from October 2017 to July 2018. Topics explored included formative sexual experiences, relationships, and experiences of HIV/STI testing. Interviews were audio-recorded, transcribed, coded, and analyzed through inductive thematic analysis. A typology comprising four distinct HIV/STI testing patterns was identified from the data, categorized based on the regularity of testing, relative to internal or external factors that motivate testing behaviors. These include triggered episodic testing, influenced episodic testing, institutionalized regular testing, and value-based regular testing. The typology highlights the preconditions that underlie different testing patterns and provides a framework for developing interventions that promote HIV/STI testing among GBQ men.

Clinics as spaces of costly disclosure: HIV/STI testing and anticipated stigma among gay, bisexual and queer men

Gay, bisexual and queer men in Singapore are disproportionately represented in prevalent HIV infections, relative to the general population. While anticipated stigma has been found to be a barrier to HIV/STI testing among gay, bisexual and queer men, little effort has been made to contextualise such stigma within the broader sociocultural milieu. We conducted 35 in-depth interviews with a purposively recruited sample of men in Singapore with a focus on topics such as sexual identity development, formative sexual experiences and HIV/STI testing experience. Interviews were analysed through thematic analysis using techniques borrowed from a grounded theory approach. Participants drew on their past interactions with family, friends, religion, the gay, bisexual and queer men's community and the wider society to construct meanings of deviance in the context of their sexuality. Participants articulated how anticipated stigma was rooted in such deviance, and how clinics or other HIV/STI-related health services served as physical spaces of costly disclosure by exposing or imposing 'deviant' identities on individuals who access these physical spaces, which were otherwise concealed. Findings from the study provide a framework for actions and interventions to address the roots of anticipated stigma in the context of HIV/STI testing among gay, bisexual and queer men.

Individual, interpersonal, and situational factors influencing HIV and other STI risk perception among gay, bisexual, and other men who have sex with men: a qualitative study

Gay, bisexual, and other men who have sex with men (GBMSM) are disproportionately affected by HIV and other sexually transmitted infections (STI). While levels of self-perceived risk of HIV or other STI acquisition has been well-established as a factor that is positively associated with HIV or other STI testing, less effort has been made to identify the processes through which GBMSM assess their perceived risk of HIV or other STI acquisition. We conducted a qualitative study exploring the factors influencing self-perceived risk of HIV or other STI among GBMSM. Semi-structured interviews were conducted with 35 self-identified GBMSM in Singapore from October 2017 to June 2018, and the data were analyzed through inductive thematic analysis. Participants reported drawing on individual factors including their own sexual health knowledge and past experiences of risk, interpersonal factors including their sexual partners' attributes or characteristics and perceived trust and familiarity with their sexual partners, and situational factors including the venue and familiarity with such venues where sexual activity took place, in determining their self-perceived risk of HIV or other STI acquisition. The results of this study have implications for HIV and other STI risk education.

Cost-Effectiveness Analysis for Influenza Vaccination Coverage and Timing in Tropical and Subtropical Climate Settings: A Modeling Study

BACKGROUND

The lack of seasonality in influenza epidemics in the tropics makes the application of well-established temperate zone national vaccination plans challenging.

OBJECTIVES

We developed an individual-based simulation model to study optimal vaccination scheduling and assess cost-effectiveness of these vaccination schedules in scenarios of no influenza seasonality and the seasonality regimes of Singapore, Taipei, and Tokyo.

METHODS

The simulation models heterogeneities in human contact networks, levels of protective antibodies following infection, the effectiveness of the influenza vaccine, and seasonality. Using a no intervention baseline, we consider 3 alternative vaccination strategies: (1) annual vaccination for a percentage of the elderly, (2) biannual vaccination for a percentage of the elderly, and (3) annual vaccination for all elderly and a fraction of the remaining population. We considered 5 vaccination uptake rates for each strategy and modeled the estimated costs, quality-adjusted life years, and incremental cost-effectiveness ratios (ICERs), indicating the cost-effectiveness of each scenario.

RESULTS

In Singapore, annual vaccination for a proportion of elderly is largely cost-effective. However, with fixed uptake rates, partial biannual vaccination for the elderly yields a higher ICER than partial annual vaccination for the elderly, resulting in a cost-ineffective ICER. The most optimal strategy is the total vaccination of all the elderly and a proportion of individuals from other age groups, which results in a cost-saving ICER. This finding is consistent across different seasonality regimes.

CONCLUSIONS

Tropical countries like Singapore can have comparably cost-effective vaccination strategies as found in countries with winter epidemics. The vaccination of all the elderly and a proportion of other age groups is the most cost-effective strategy, supporting the need for an extensive national influenza vaccination program.

Cost and anonymity as factors for the effective implementation of pre-exposure prophylaxis: an observational study among gay, bisexual and other men who have sex with men in Singapore

Background HIV pre-exposure prophylaxis (PrEP) is currently offered by several public and private clinics at unsubsidised prices in Singapore, but to date, no information is available on the effect of these services. This study sought to assess the knowledge and uptake of, and willingness to use PrEP among gay, bisexual and other men who have sex with men (GBMSM) in Singapore.

METHODS

Recruitment was conducted through Grindr®, a geosocial networking application for GBMSM. Results were quantitatively analysed through descriptive statistics and multivariate Poisson regression models, while open-ended responses were qualitatively coded and categorised.

RESULTS

Of the 1339 participants who responded, 1098 participants who indicated their knowledge and use of PrEP were included in the analytic sample. Overall, 15.0% (n=154) had taken PrEP, 66.2% (n=678) had heard of but not taken PrEP, while 18.8% (n=193) had never heard of PrEP. Of those who had ever taken PrEP, 59.6% (n=90) had obtained PrEP from overseas or other unofficial sources. Of those who had heard of but never taken PrEP, 73.3% (n=486) reported that they would consider taking PrEP. Those who had taken PrEP were older and had higher educational attainment.

CONCLUSIONS

The gap between the willingness to use PrEP and its uptake may be attributed to the cost of PrEP and issues of anonymity at healthcare settings in Singapore. National financing schemes are needed to expand access to PrEP if it is to make a meaningful effect to the Singapore HIV/AIDS response.

Passive immune therapy and other immunomodulatory agents for the treatment of severe influenza: Systematic review and meta-analysis

BACKGROUND

A range of immunomodulatory therapies have been proposed as adjuncts to conventional antivirals to suppress harmful inflammation during severe influenza infection. We conducted a systematic review to assess available data of the effect of adjunctive non-corticosteroid immunomodulatory therapy and potential adverse effects.

METHOD

We searched MEDLINE, Embase, Web of Science and clinical trial databases for published and unpublished studies, and screened the references of included articles. We included RCTs, quasi-RCTs and observational studies of virologically confirmed influenza infections in hospitalised patients. We did not restrict studies by language of publication, influenza type/subtype or age of participants. Where possible, we pooled estimates of effect using random-effects meta-analysis models.

RESULTS

We identified 11 eligible studies for inclusion: five studies (4 RCTs and 1 observational; 693 individuals) of passive immune therapy; four studies (3 RCTs and 1 observational; 1120 individuals) of macrolides and/or non-steroidal anti-inflammatory drugs (NSAIDs), one RCT of mTOR inhibitors (38 individuals), and one RCT of statin therapy (116 individuals). Meta-analysis of RCTs of passive immune therapy indicated no significant reduction in mortality (OR 0.84, 0.37-1.90), but better clinical outcomes at Day 7 (OR 1.42, 1.05-1.92). There was a significant reduction in mortality associated with macrolides and/or NSAIDs (OR 0.28; 0.10-0.77).

CONCLUSIONS

Passive immune therapy is unlikely to offer substantial mortality benefit in treatment of severe seasonal influenza, but may improve clinical outcomes. The effect of other immunomodulatory agents is uncertain, but promising. There is a need for high-quality RCTs with sufficient statistical power to address this evidence gap.

Accuracy of urinary symptoms and urine microscopy in diagnosing urinary tract infection in women

BACKGROUND

Women with urinary tract infections (UTIs) often present with urinary complaints such as frequency of micturition, dysuria, foul-smelling urine and other non-specific symptoms like fever. Physicians may order urine microscopy to guide empirical antibiotic prescription. However, the performance of this approach has not been assessed.

OBJECTIVES

This study aimed to determine the accuracy of UTI symptoms and urine microscopy associated with culture-positive UTI in Asian women.

METHODS

A cross-sectional study of adult women who presented with UTI-related symptoms was conducted at three public primary care clinics in Singapore. Demographic data and information on their symptoms were collected, followed by urine microscopy and culture to diagnose UTI. The sensitivity, specificity, positive (PPV), negative predictive values (NPV), accuracy (ACC) and area under curve (AUC) of combinations of symptom and urine investigations were analysed in association with culture-positive UTI, which was regarded as a benchmark.

RESULTS

Data on 564 women (73.9% Chinese, 11.5% Malay, 8.2% Indian) were analysed, of which 259 (45.9%) had culture-positive UTI. Frequency and foul-smelling urine, pyuria (WBC ≥10/hpf) and semi-quantitative bacterial count (≥2+) were significantly associated with positive urine culture. The ACC and AUC for single or multiple urinary and/or general symptoms were low. Urine pyuria (minimally >10/hpf) alone or in combination with symptoms and/or semi-quantitative bacterial count achieved high sensitivity (>85%) and PPV, NPV, ACC and AUC of >70%.

CONCLUSION

Urinary symptoms have limited accuracy in diagnosing culture-positive UTI. Concurrent urine microscopy showing presence of pyuria and/or bacterial count increased the diagnostic accuracy of culture-positive UTI.

Utility of Spatial Point-Pattern Analysis Using Residential and Workplace Geospatial Information to Localize Potential Outbreak Sources

Identifying the source of an outbreak facilitates its control. Spatial methods are not optimally used in outbreak investigation, due to a mix of the complexities involved (e.g., methods requiring additional parameter selection), imperfect performance, and lack of confidence in existing options. We simulated 30 mock outbreaks and compared 5 simple methods that do not require parameter selection but could select between mock cases’ residential and workplace addresses to localize the source. Each category of site had a unique spatial distribution; residential and workplace address were visually and statistically clustered around the residential neighborhood and city center sites respectively, suggesting that the value of workplace addresses is tied to the location where an outbreak might originate. A modification to centrographic statistics that we propose—the center of minimum geometric distance with address selection—was able to localize the mock outbreak source to within a 500 m radius in almost all instances when using workplace in combination with residential addresses. In the sensitivity analysis, when given sufficient workplace data, the method performed well in various scenarios with only 10 cases. It was also successful when applied to past outbreaks, except for a multisite outbreak from a common food supplier.

Duration of Influenza Vaccine Effectiveness: A Systematic Review, Meta-analysis, and Meta-regression of Test-Negative Design Case-Control Studies

Background

Whether influenza vaccination offers protection for the duration of an influenza season was called into question recently after analysis of data from test-negative design (TND) case-control studies.

Method

The published literature was systematically reviewed to identify TND studies that estimated the change in vaccine effectiveness (VE) with respect to time since vaccination.

Results

Fourteen studies were identified through the literature search as meeting eligibility criteria. Meta-analyses were performed to compare VE 15-90 days after vaccination to VE 91-180 days after vaccination. A significant decline in VE was observed for influenza virus subtype A/H3 (change in VE, -33; 95% confidence interval [CI], -57 to -12) and type B (change in VE, -19; 95% CI, -33 to -6). VE declined for influenza virus subtype A/H1, but this difference was not statistically significant (change in VE -8; 95% CI, -27 to 21). A multivariable mixed-effects meta-regression model indicated that the change VE was associated with the proportion of study participants who were cases and the proportion who were vaccinated controls (P < .05). This could reflect biological effects such as (1) mismatch between the vaccine received and the circulating strains (among cases), (2) herd immunity (among controls), or (3) the reduced power of individual TND studies in the later parts of an influenza outbreak.

Conclusions

Exploration of new influenza vaccination strategies must be a priority for influenza control, particularly in tropical countries with year-round influenza virus activity.

Extent and selectivity of sexual orientation disclosure and its association with HIV and other STI testing patterns among gay, bisexual and other men who have sex with men

Objectives

Gay, bisexual and other men who have sex with men (GBMSM) in Singapore may fear disclosing their sexual orientation to others due to negative societal attitudes, and the law that criminalises sexual relations between men, which may, in turn, impede access to HIV/sexually transmitted infection (STI)-related health services. This study attempts to determine how selective disclosure to varying social groups, and the extent of disclosure, may serve to impact HIV/STI testing patterns among GBMSM.

Methods

In this observational study, we recruited GBMSM in Singapore through an online cross-sectional survey disseminated via the smartphone app Grindr from 14 January to 11 February 2018. Respondents provided information on their sociodemographic characteristics, disclosure of sexual orientation towards other lesbian, gay, bisexual, transgender and questioning (LGBTQ) individuals, non-LGBTQ family members, non-LGBTQ friends and non-LGBTQ colleagues, along with their HIV/STI testing patterns. Extent of disclosure was defined as the number of social groups that a participant had disclosed his sexual orientation to. Statistical analyses were conducted through descriptive statistics, multivariable binary, ordinal, and multinomial logistic regression models.

Results

We recruited 1339 respondents, of which 1098 who had provided their response to questions on HIV/STI testing were included in the analytic sample. Multivariable analyses indicated that disclosure towards non-LGBTQ family members (adjusted OR [aOR] 1.85, 95% CI 1.12 to 3.07) and other LGBTQ individuals (aOR 1.63, 95% CI 1.12 to 2.37) were positively associated with recent HIV testing, whereas disclosure towards non-LGBTQ colleagues (aOR 1.56, 95% CI 1.09 to 2.22) was positively associated with regular HIV testing. Extent of disclosure exhibited a positive, dose–response relationship with all testing outcomes.

Conclusions

Results indicate how the fear of being identified as an LGBTQ individual may deter GBMSM from getting tested for HIV and other STIs. Health services should bridge the gaps to accessing healthcare among individuals who fear being stigmatised for attending sexual health-specific clinics or being identified as GBMSM.

Chemsex among gay, bisexual, and other men who have sex with men in Singapore and the challenges ahead: A qualitative study

BACKGROUND

Sexualised substance use, or 'chemsex' has been shown to be a major factor driving the syndemic of HIV/AIDS in communities of gay, bisexual, and other men who have sex with men (GBMSM) around the world. However, there is a paucity of research on chemsex among GBMSM in Singapore due to punitive drug laws and the criminalisation of sexual behaviour between men. This qualitative descriptive study is the first to explore perceptions towards, motivators to engaging in, and the barriers to addressing the harms associated with chemsex among GBMSM in Singapore.

METHODS

We conducted 30 semi-structured in-depth interviews with self-identifying GBMSM between the ages of 18-39 in Singapore following a purposive sampling strategy. Interview topics included participants' perceptions of drug use among GBMSM in Singapore, perceptions towards chemsex, reasons for drug use and chemsex, and recommendations to address the harms associated with chemsex in Singapore. Interviews were audio-recorded, transcribed, coded, and analysed using thematic analysis.

RESULTS

Participants reported that it was common to encounter chemsex among GBMSM in Singapore as it could be easily accessed or initiated using social networking phone apps. Enhancement and prolongation of sexual experiences, fear of rejection from sexual partners and peers, and its use as a means of coping with societal rejection were three main reasons cited for engaging in chemsex. The impact of punitive drug laws on disclosure and stigmatisation of GBMSM who use drugs were reported to be key barriers towards addressing chemsex. Participants suggested using gay-specific commercial venues as avenues for awareness and educational campaigns, and social media to reach out to younger GBMSM.

CONCLUSIONS

This study highlights the complexities behind chemsex use among GBMSM in Singapore, and the range of individual to institutional factors to be addressed. We recommend that community-based organisations and policy-makers find ways to destigmatise discussion of chemsex and provide safe spaces to seek help for drug use.

Epidemiology and Relative Severity of Influenza Subtypes in Singapore in the Post-Pandemic Period from 2009 to 2010

Background

After 2009, pandemic influenza A(H1N1) [A(H1N1)pdm09] cocirculated with A(H3N2) and B in Singapore.

Methods

A cohort of 760 participants contributed demographic data and up to 4 blood samples each from October 2009 to September 2010. We compared epidemiology of the 3 subtypes and investigated evidence for heterotypic immunity through multivariable logistic regression using a generalized estimating equation. To examine age-related differences in severity between subtypes, we used LOESS (locally weighted smoothing) plots of hospitalization to infection ratios and explored birth cohort effects referencing the pandemic years (1957; 1968).

Results

Having more household members aged 5–19 years and frequent public transport use increased risk of infection, while preexisting antibodies against the same subtype (odds ratio [OR], 0.61; P = .002) and previous influenza infection against heterotypic infections (OR, 0.32; P = .045) were protective. A(H1N1)pdm09 severity peaked in those born around 1957, while A(H3N2) severity was least in the youngest individuals and increased until it surpassed A(H1N1)pdm09 in those born in 1952 or earlier. Further analysis showed that severity of A(H1N1)pdm09 was less than that for A(H3N2) in those born in 1956 or earlier (P = .021) and vice versa for those born in 1968 or later (P < .001), with no difference in those born between 1957 and 1967 (P = .632).

Conclusions

Our findings suggest that childhood exposures had long-term impact on immune responses consistent with the theory of antigenic sin. This, plus observations on short-term cross-protection, have implications for vaccination and influenza epidemic and pandemic mitigation strategies.

Validation of a Natural Language Processing Algorithm for Detecting Infectious Disease Symptoms in Primary Care Electronic Medical Records in Singapore

Background

Free-text clinical records provide a source of information that complements traditional disease surveillance. To electronically harness these records, they need to be transformed into codified fields by natural language processing algorithms.

Objective

The aim of this study was to develop, train, and validate Clinical History Extractor for Syndromic Surveillance (CHESS), an natural language processing algorithm to extract clinical information from free-text primary care records.

Methods

CHESS is a keyword-based natural language processing algorithm to extract 48 signs and symptoms suggesting respiratory infections, gastrointestinal infections, constitutional, as well as other signs and symptoms potentially associated with infectious diseases. The algorithm also captured the assertion status (affirmed, negated, or suspected) and symptom duration.

Electronic medical records from the National Healthcare Group Polyclinics, a major public sector primary care provider in Singapore, were randomly extracted and manually reviewed by 2 human reviewers, with a third reviewer as the adjudicator. The algorithm was evaluated based on 1680 notes against the human-coded result as the reference standard, with half of the data used for training and the other half for validation.

Results

The symptoms most commonly present within the 1680 clinical records at the episode level were those typically present in respiratory infections such as cough (744/7703, 9.66%), sore throat (591/7703, 7.67%), rhinorrhea (552/7703, 7.17%), and fever (928/7703, 12.04%). At the episode level, CHESS had an overall performance of 96.7% precision and 97.6% recall on the training dataset and 96.0% precision and 93.1% recall on the validation dataset. Symptoms suggesting respiratory and gastrointestinal infections were all detected with more than 90% precision and recall. CHESS correctly assigned the assertion status in 97.3%, 97.9%, and 89.8% of affirmed, negated, and suspected signs and symptoms, respectively (97.6% overall accuracy). Symptom episode duration was correctly identified in 81.2% of records with known duration status.

Conclusions

We have developed an natural language processing algorithm dubbed CHESS that achieves good performance in extracting signs and symptoms from primary care free-text clinical records. In addition to the presence of symptoms, our algorithm can also accurately distinguish affirmed, negated, and suspected assertion statuses and extract symptom durations.

Adequacy of public health communications on H7N9 and MERS in Singapore: insights from a community based cross-sectional study

Background

Singapore remains vulnerable to worldwide epidemics due to high air traffic with other countries This study aims to measure the public’s awareness of the Middle East Respiratory Syndrome (MERS) and Avian Influenza A (H7N9), identify population groups who are uninformed or misinformed about the diseases, understand their choice of outbreak information source, and assess the effectiveness of communication channels in Singapore.

Methods

A cross-sectional study, comprising of face-to-face interviews, was conducted between June and December 2013 to assess the public’s awareness and knowledge of MERS and H7N9, including their choice of information source. Respondents were randomly selected and recruited from 3 existing cohort studies. An opportunistic sampling approach was also used to recruit new participants or members in the same household through referrals from existing participants.

Results

Out of 2969 participants, 53.2% and 79.4% were not aware of H7N9 and MERS respectively. Participants who were older and better educated were most likely to hear about the diseases. The mean total knowledge score was 9.2 (S.D ± 2.3) out of 20, and 5.9 (S.D ± 1.2) out of 10 for H7N9 and MERS respectively. Participants who were Chinese, more educated and older had better knowledge of the diseases. Television and radio were the primary sources of outbreak information regardless of socio-demographic factors.

Conclusion

Heightening education of infectious outbreaks through appropriate media to the young and less educated could increase awareness.

Severity and burden of hand, foot and mouth disease in Asia: a modelling study

Background

Hand, foot and mouth disease (HFMD) affects millions of children across Asia annually, leading to an increase in implemented control policies such as surveillance, isolation and social distancing in affected jurisdictions. However, limited knowledge of disease burden and severity causes difficulty in policy optimisation as the associated economic cost cannot be easily estimated. We use a data synthesis approach to provide a comprehensive picture of HFMD disease burden, estimating infection risk, symptomatic rates, the risk of complications and death, and overall disability-adjusted life-year (DALY) losses, along with associated uncertainties.

Methods

Complementary data from a variety of sources were synthesised with mathematical models to obtain estimates of severity of HFMD. This includes serological and other data extracted through a systematic review of HFMD epidemiology previously published by the authors, and laboratory investigations and sentinel reports from Singapore's surveillance system.

Results

HFMD is estimated to cause 96 900 (95% CI 40 600 to 259 000) age-weighted DALYs per annum in eight high-burden countries in East and Southeast Asia, with the majority of DALYs attributed to years of life lost. The symptomatic case hospitalisation rate of HFMD is 6% (2.8%-14.9%), of which 18.7% (6.7%-31.5%) are expected to develop complications. 5% (2.9%-7.4%) of such cases are fatal, bringing the overall case fatality ratio to be 52.3 (24.4-92.7) per 100 000 symptomatic infections. In contrast, the EV-A71 case fatality ratio is estimated to be at least 229.7 (75.4-672.1) per 100 000 symptomatic cases. Asymptomatic rate for EV-A71 is 71.4% (68.3%-74.3%) for ages 1-4, the years of greatest incidence.

Conclusion

Despite the high incidence rate of HFMD, total DALY due to HFMD is limited in comparison to other endemic diseases in the region, such as dengue and upper respiratory tract infection. With the majority of DALY caused by years of life lost, it is possible to mitigate most with increased EV-A71 vaccine coverage.

Individual and Population Trajectories of Influenza Antibody Titers Over Multiple Seasons in a Tropical Country

Seasonal influenza epidemics occur year-round in the tropics, complicating the planning of vaccination programs. We built an individual-level longitudinal model of baseline antibody levels, time of infection, and the subsequent rise and decay of antibodies postinfection using influenza A(H1N1)pdm09 data from 2 sources in Singapore: 1) a noncommunity cohort with real-time polymerase chain reaction–confirmed infections and at least 1 serological sample collected from each participant between May and October 2009 (n = 118) and 2) a community cohort with up to 6 serological samples collected between May 2009 and October 2010 (n = 760). The model was hierarchical, to account for interval censoring and interindividual variation. Model parameters were estimated via a reversible jump Markov chain Monte Carlo algorithm using custom-designed R (https://www.r-project.org/) and C++ (https://isocpp.org/) code. After infection, antibody levels peaked at 4–7 weeks, with a half-life of 26.5 weeks, followed by a slower decrease up to 1 year to approximately preinfection levels. After the third wave, the seropositivity rate and the population-level antibody titer dropped to the same level as they were at the end of the first pandemic wave. The results of this analysis are consistent with the hypothesis that the population-level effect of individuals’ waxing and waning antibodies influences influenza seasonality in the tropics.

Infectious disease transmission: survey of contacts between hospital-based healthcare workers and working adults from the general population

BACKGROUND

Healthcare workers (HCWs) may be the inadvertent interface between the healthcare setting and the community for infectious diseases transmission.

AIM

To investigate HCWs' contacts during a work day and compare these against working adults from the general population.

METHODS

Prospective survey of contacts through 24 h self-reported diary in three public sector tertiary care hospitals and community-based working adults in Singapore. Participants were HCWs and working adults from the community.

FINDINGS

In all, 211 HCWs and 1028 working adults reported a total of 4066 and 9206 contacts. HCWs reported more work-related contacts than community-based working adults (median of 13 versus 4), and more contacts that were neither household nor work-related (1 versus 0) but fewer household contacts (2 versus 3). HCWs reported more work-related contacts involving physical contacts, and more new contacts particularly with short duration (≤15 min) compared to community-based working adults. Among different HCW types, doctors reported the highest whereas ward-based nurses reported the lowest total work-related contacts. Around half of ward-based and clinic-based nurses' contacts involved physical touch. Work-related contacts reported by clinic-based nurses, doctors, and assorted HCWs were shorter than in ward-based nurses, with a substantial number effectively occurring with new contacts. Institutional effects significant on univariate analyses were much reduced and non-significant after adjusting for confounding by HCW type.

CONCLUSION

HCWs' contacts differ substantially from those of community-based working adults. HCWs may thus be at higher risk of acquiring and spreading contact-transmissible and respiratory infections due to the nature of their work. Whereas total number of contacts was fairly similar between HCW types, the characteristics of their contacts differed substantively.

Using peer review to distribute group work marks equitably between medical students

BACKGROUND

Although peer assessment has been used for evaluating performance of medical students and practicing doctors, it has not been studied as a method to distribute a common group work mark equitably to medical students working in large groups where tutors cannot observe all students constantly.

METHODS

The authors developed and evaluated a mathematical formulation whereby a common group mark could be distributed among group members using peer assessment of individual contributions to group work, maintaining inter-group variation in group work scores. This was motivated by community health projects undertaken by large groups of year four medical students at the National University of Singapore, and the new and old formulations are presented via application to 263 students in seven groups of 36 to 40 during the academic year 2012/2013.

RESULTS

This novel formulation produced a less clustered mark distribution that rewarded students who contributed more to their team. Although collusion among some members to form a voting alliance and 'personal vendettas' were potential problems, the former was not detected and the latter had little impact on the overall grade a student received when working in a large group. The majority of students thought the new formulation was fairer.

CONCLUSIONS

The new formulation is easy to implement and arguably awards grades more equitably in modules where group work is a major component.

Rethinking thresholds for serological evidence of influenza virus infection

Introduction

For pathogens such as influenza that cause many subclinical cases, serologic data can be used to estimate attack rates and the severity of an epidemic in near real time. Current methods for analysing serologic data tend to rely on use of a simple threshold or comparison of titres between pre‐ and post‐epidemic, which may not accurately reflect actual infection rates.

Methods

We propose a method for quantifying infection rates using paired sera and bivariate probit models to evaluate the accuracy of thresholds currently used for influenza epidemics with low and high existing herd immunity levels, and a subsequent non‐influenza period. Pre‐ and post‐epidemic sera were taken from a cohort of adults in Singapore (n=838). Bivariate probit models with latent titre levels were fit to the joint distribution of haemagglutination‐inhibition assay‐determined antibody titres using Markov chain Monte Carlo simulation.

Results

Estimated attack rates were 15% (95% credible interval: 12%‐19%) for the first H1N1 pandemic wave. For a large outbreak due to a new strain, a threshold of 1:20 and a twofold rise (if pared sera is available) would result in a more accurate estimate of incidence.

Conclusion

The approach presented here offers the basis for a reconsideration of methods used to assess diagnostic tests by both reconsidering the thresholds used and by analysing serological data with a novel statistical model.

Detection of viral respiratory pathogens in mild and severe acute respiratory infections in Singapore

To investigate the performance of laboratory methods and clinical case definitions in detecting the viral pathogens for acute respiratory infections (ARIs) from a prospective community cohort and hospital inpatients, nasopharyngeal swabs from cohort members reporting ARIs (community-ARI) and inpatients admitted with ARIs (inpatient-ARI) were tested by Singleplex Real Time-Polymerase Chain Reaction (SRT-PCR), multiplex RT-PCR (MRT-PCR) and pathogen-chip system (PathChip) between April 2012 and December 2013. Community-ARI and inpatient-ARI was also combined with mild and severe cases of influenza from a historical prospective study as mild-ARI and severe-ARI respectively to evaluate the performance of clinical case definitions. We analysed 130 community-ARI and 140 inpatient-ARI episodes (5 inpatient-ARI excluded because multiple pathogens were detected), involving 138 and 207 samples respectively. Detection by PCR declined with days post-onset for influenza virus; decrease was faster for community-ARI than for inpatient-ARI. No such patterns were observed for non-influenza respiratory virus infections. PathChip added substantially to viruses detected for community-ARI only. Clinical case definitions discriminated influenza from other mild-ARI but performed poorly for severe-ARI and for older participants. Rational strategies for diagnosis and surveillance of influenza and other respiratory virus must acknowledge the differences between ARIs presenting in community and hospital settings.

The immune response to 6-monthly versus annual standard dose inactivated trivalent influenza vaccination in older people: study protocol for a randomised clinical trial

Background

The seasonal influenza vaccine is less effective in older people and a single dose is unlikely to provide the year-round protection necessary for tropical climates which have year-round influenza virus activity. This study aims to assess the effect of a trivalent inactivated influenza vaccine (IIV3) booster at 180 days on haemagglutination-inhibition (HI) antibody titres for each of the influenza strains present in the administered vaccine in older people aged 65 years or above in Singapore.

Methods/design

This is a single-centre, randomised, observer-blind, active-comparator controlled, parallel-group, phase IV trial in 200 adults aged 65 years or older. Study participants will be assigned to one of two groups in a 1:1 ratio and followed for 1 year, with five scheduled visits. The control group will receive IIV3 at day 1, and an active comparator (Tetanus-diphtheria-pertussis vaccine) at day 180. Participants in the experimental group will receive IIV3 containing the same strains at day 1 and day 180. Endpoints are immunological, and include measures of HI titres, microneutralisation titres (MN) and cell-mediated immunity from first vaccination up to day 360.

Discussion

If superiority of 6-monthly influenza vaccination is demonstrated, this study could form the basis for a larger clinical trial with influenza infection as the primary endpoint.

Trial registration

ClinicalTrials.gov, ID: NCT02655874. Registered on 12 January 2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-1808-8) contains supplementary material, which is available to authorized users.

Knowledge, attitudes and practices towards antibiotic use in upper respiratory tract infections among patients seeking primary health care in Singapore

Background

Patients’ expectations can influence antibiotic prescription by primary healthcare physicians. We assessed knowledge, attitude and practices towards antibiotic use for upper respiratory tract infections (URTIs), and whether knowledge is associated with increased expectations for antibiotics among patients visiting primary healthcare services in Singapore.

Methods

Data was collected through a cross-sectional interviewer-assisted survey of patients aged ≥21 years waiting to see primary healthcare practitioners for one or more symptoms suggestive of URTI (cough, sore throat, runny nose or blocked nose) for 7 days or less, covering the demographics, presenting symptoms, knowledge, attitudes, beliefs and practices of URTI and associated antibiotic use. Univariate and multivariate logistic regression was used to assess independent factors associated with patients’ expectations for antibiotics.

Results

Nine hundred fourteen out of 987 eligible patients consulting 35 doctors were recruited from 24 private sector primary care clinics in Singapore. A third (307/907) expected antibiotics, of which a substantial proportion would ask the doctor for antibiotics (121/304, 40 %) and/or see another doctor (31/304, 10 %) if antibiotics were not prescribed. The majority agreed “antibiotics are effective against viruses” (715/914, 78 %) and that “antibiotics cure URTI faster” (594/912, 65 %). Inappropriate antibiotic practices include “keeping antibiotics stock at home” (125/913, 12 %), “taking leftover antibiotics” (114/913, 14 %) and giving antibiotics to family members (62/913, 7 %). On multivariate regression, the following factors were independently associated with wanting antibiotics (odds ratio; 95 % confidence interval): Malay ethnicity (1.67; 1.00–2.79), living in private housing (1.69; 1.13–2.51), presence of sore throat (1.50; 1.07–2.10) or fever (1.46; 1.01–2.12), perception that illness is serious (1.70; 1.27–2.27), belief that antibiotics cure URTI faster (5.35; 3.76–7.62) and not knowing URTI resolves on its own (2.18; 1.08–2.06), while post-secondary education (0.67; 0.48–0.94) was inversely associated. Those with lower educational levels were significantly more likely to have multiple misconceptions about antibiotics.

Conclusion

Majority of patients seeking primary health care in Singapore are misinformed about the role of antibiotics in URTI. Agreeing with the statement that antibiotics cure URTI faster was most strongly associated with wanting antibiotics. Those with higher educational levels were less likely to want antibiotics, while those with lower educational levels more likely to have incorrect knowledge.

Electronic supplementary material

The online version of this article (doi:10.1186/s12875-016-0547-3) contains supplementary material, which is available to authorized users.

Rate of decline of antibody titers to pandemic influenza A (H1N1-2009) by hemagglutination inhibition and virus microneutralization assays in a cohort of seroconverting adults in Singapore

Background

The rate of decline of antibody titers to influenza following infection can affect results of serological surveys, and may explain re-infection and recurrent epidemics by the same strain.

Methods

We followed up a cohort who seroconverted on hemagglutination inhibition (HI) antibody titers (≥4-fold increase) to pandemic influenza A(H1N1)pdm09 during a seroincidence study in 2009. Along with the pre-epidemic sample, and the sample from 2009 with the highest HI titer between August and October 2009 (A), two additional blood samples obtained in April 2010 and September 2010 (B and C) were assayed for antibodies to A(H1N1)pdm09 by both HI and virus microneutralization (MN) assays. We analyzed pair-wise mean-fold change in titers and the proportion with HI titers ≥ 40 and MN ≥ 160 (which correlated with a HI titer of 40 in our assays) at the 3 time-points following seroconversion.

Results

A total of 67 participants contributed 3 samples each. From the highest HI titer in 2009 to the last sample in 2010, 2 participants showed increase in titers (by HI and MN), while 63 (94%) and 49 (73%) had reduction in HI and MN titers, respectively. Titers by both assays decreased significantly; while 70.8% and 72.3% of subjects had titers of ≥ 40 and ≥ 160 by HI and MN in 2009, these percentages decreased to 13.9% and 36.9% by September 2010. In 6 participants aged 55 years and older, the decrease was significantly greater than in those aged below 55, so that none of the elderly had HI titers ≥ 40 nor MN titers ≥ 160 by the final sample. Due to this decline in titers, only 23 (35%) of the 65 participants who seroconverted on HI in sample A were found to seroconvert between the pre-epidemic sample and sample C, compared to 53 (90%) of the 59 who seroconverted on MN on Sample A.

Conclusions

We observed marked reduction in titers 1 year after seroconversion by HI, and to a lesser extent by MN. Our findings have implications for re-infections, recurrent epidemics, vaccination strategies, and for cohort studies measuring infection rates by seroconversion.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2334-14-414) contains supplementary material, which is available to authorized users.

Health-seeking behaviour of male foreign migrant workers living in a dormitory in Singapore

Background

Foreign workers’ migrant status may hinder their utilisation of health services. This study describes the health-seeking behaviour and beliefs of a group of male migrant workers in Singapore and the barriers limiting their access to primary healthcare.

Methods

A cross-sectional study of 525 male migrant workers, ≥21 years old and of Indian, Bangladeshi or Myanmar nationality, was conducted at a dormitory via self-administered questionnaires covering demographics, prevalence of medical conditions and health-seeking behaviours through hypothetical scenarios and personal experience.

Results

71% (95%CI: 67 to 75%) of participants did not have or were not aware if they had healthcare insurance. 53% (95%CI: 48 to 57%) reported ever having had an illness episode while in Singapore, of whom 87% (95%CI: 82 to 91%) saw a doctor. The number of rest days was significantly associated with higher probability of having consulted a doctor for their last illness episode (p = 0.026), and higher basic monthly salary was associated with seeing a doctor within 3 days of illness (p = 0.002). Of those who saw a doctor, 84% (95%CI: 79 to 89%) responded that they did so because they felt medical care would help them to work better. While 55% (95%CI: 36 to 73%) said they did not see a doctor because the illness was not serious, those with lower salaries were significantly more likely to cite inadequate finances (55% of those earning < S$500/month). In hypothetical injury or illness scenarios, most responded that they would see the doctor, but a sizeable proportion (15% 95%CI: 12 to 18%) said they would continue to work even in a work-related injury scenario that caused severe pain and functional impairment. Those with lower salaries were significantly more likely to believe they would have to pay for their own healthcare or be uncertain about who would pay.

Conclusions

The majority of foreign workers in this study sought healthcare when they fell ill. However, knowledge about health-related insurance was poor and a sizeable minority, in particular those earning < S$500 per month, may face significant issues in accessing care.

Respiratory viral pathogens among Singapore military servicemen 2009-2012: epidemiology and clinical characteristics

Background

Few studies have comprehensively described tropical respiratory disease surveillance in military populations. There is also a lack of studies comparing clinical characteristics of the non-influenza pathogens with influenza and amongst themselves.

Methods

From May 2009 through October 2012, 7733 consenting cases of febrile respiratory illness (FRI) (temperature [greater than or equal to]37.5degreesC with cough or sorethroat) and controls in the Singapore military had clinical data and nasal washes collected prospectively. Nasal washes underwent multiplex PCR, and the analysis was limited to viral mono-infections.

Results

49% of cases tested positive for at least one virus, of whom 10% had multiple infections. 53% of the FRI cases fulfilled the definition of influenza-like illness (ILI), of whom 52% were positive for at least one virus. The most frequent etiologies for mono-infections among FRI cases were Influenza A(H1N1)pdm09 (13%), Influenza B (13%) and coxsackevirus (9%). The sensitivity, specificity, positive predictive value and negative predictive value of ILI for influenza among FRI cases were 72%, 48%, 40% and 69% respectively. On logistic regression, there were marked differences in the prevalence of different symptoms and signs between viruses with fever more prevalent amongst influenza and adenovirus infections than other viruses.

Conclusion

There are multiple viral etiologies for FRI and ILI with differing clinical symptoms in the Singapore military. Influenza and coxsackevirus were the most common etiology for FRI, while influenza and adenoviruses displayed the most febrile symptoms. Further studies should explore these differences and possible interventions.

Comparability of results from pair and classical model formulations for different sexually transmitted infections

The "classical model" for sexually transmitted infections treats partnerships as instantaneous events summarized by partner change rates, while individual-based and pair models explicitly account for time within partnerships and gaps between partnerships. We compared predictions from the classical and pair models over a range of partnership and gap combinations. While the former predicted similar or marginally higher prevalence at the shortest partnership lengths, the latter predicted self-sustaining transmission for gonorrhoea (GC) and Chlamydia (CT) over much broader partnership and gap combinations. Predictions on the critical level of condom use (C(c)) required to prevent transmission also differed substantially when using the same parameters. When calibrated to give the same disease prevalence as the pair model by adjusting the infectious duration for GC and CT, and by adjusting transmission probabilities for HIV, the classical model then predicted much higher C(c) values for GC and CT, while C(c) predictions for HIV were fairly close. In conclusion, the two approaches give different predictions over potentially important combinations of partnership and gap lengths. Assuming that it is more correct to explicitly model partnerships and gaps, then pair or individual-based models may be needed for GC and CT since model calibration does not resolve the differences.

Real-time epidemic monitoring and forecasting of H1N1-2009 using influenza-like illness from general practice and family doctor clinics in Singapore

Background

Reporting of influenza-like illness (ILI) from general practice/family doctor (GPFD) clinics is an accurate indicator of real-time epidemic activity and requires little effort to set up, making it suitable for developing countries currently experiencing the influenza A (H1N1 -2009) pandemic or preparing for subsequent epidemic waves.

Methodology/Principal Findings

We established a network of GPFDs in Singapore. Participating GPFDs submitted returns via facsimile or e-mail on their work days using a simple, standard data collection format, capturing: gender; year of birth; “ethnicity”; residential status; body temperature (°C); and treatment (antiviral or not); for all cases with a clinical diagnosis of an acute respiratory illness (ARI). The operational definition of ILI in this study was an ARI with fever of 37.8°C or more. The data were processed daily by the study co-ordinator and fed into a stochastic model of disease dynamics, which was refitted daily using particle filtering, with data and forecasts uploaded to a website which could be publicly accessed. Twenty-three GPFD clinics agreed to participate. Data collection started on 2009-06-26 and lasted for the duration of the epidemic. The epidemic appeared to have peaked around 2009-08-03 and the ILI rates had returned to baseline levels by the time of writing.

Conclusions/Significance

This real-time surveillance system is able to show the progress of an epidemic and indicates when the peak is reached. The resulting information can be used to form forecasts, including how soon the epidemic wave will end and when a second wave will appear if at all.

Influenza excess mortality from 1950-2000 in tropical Singapore

Introduction

Tropical regions have been shown to exhibit different influenza seasonal patterns compared to their temperate counterparts. However, there is little information about the burden of annual tropical influenza epidemics across time, and the relationship between tropical influenza epidemics compared with other regions.

Methods

Data on monthly national mortality and population was obtained from 1947 to 2003 in Singapore. To determine excess mortality for each month, we used a moving average analysis for each month from 1950 to 2000. From 1972, influenza viral surveillance data was available. Before 1972, information was obtained from serial annual government reports, peer-reviewed journal articles and press articles.

Results

The influenza pandemics of 1957 and 1968 resulted in substantial mortality. In addition, there were 20 other time points with significant excess mortality. Of the 12 periods with significant excess mortality post-1972, only one point (1988) did not correspond to a recorded influenza activity. For the 8 periods with significant excess mortality periods before 1972 excluding the pandemic years, 2 years (1951 and 1953) had newspaper reports of increased pneumonia deaths. Excess mortality could be observed in almost all periods with recorded influenza outbreaks but did not always exceed the 95% confidence limits of the baseline mortality rate.

Conclusion

Influenza epidemics were the likely cause of most excess mortality periods in post-war tropical Singapore, although not every epidemic resulted in high mortality. It is therefore important to have good influenza surveillance systems in place to detect influenza activity.

An assessment of electronically captured data in the patient care enhancement system (PACES) for syndromic surveillance

INTRODUCTION

A common approach to the surveillance of emerging infectious diseases and agents of bioterrorism is to analyse electronically captured data for disease syndromes. The Patient Care Enhancement System (PACES) is a form of electronic medical records presently in service in the Singapore Armed Forces (SAF). We assess the feasibility of PACES data for surveillance, describe time-trends, and identify methods of sub-analysis which could improve performance.

MATERIALS AND METHODS

Medical consults from July 2000 to June 2003 were extracted. Diagnosis codes were mapped to 7 infectious disease syndromes according to the categorisation in the Electronic Surveillance System for the Early Notification of Community-based Epidemics (ESSENCE): gastrointestinal (GI), fever (FEVER), respiratory, (RESP), coma (COMA), neurological (NEURO), dermatologic-haemorrhagic (DERMHEM) and dermatologic- infectious (DERM-INF).

RESULTS

A total of 732,233 episodes of care were analysed. Weekly periodicity was observed, with decreased weekend consults; there were no obvious seasonal trends in any of the syndromes. RESP, FEVER and GI syndromes were common events. Sub-analyses, either by restricting to cases with a repeated consultation, or grouping the data by medical centres, could dramatically lower thresholds used to flag outbreaks.

CONCLUSION

In spite of the level of background noise inherent in a system consisting mainly of primary care consults, sub-analysis by medical centre, or restriction to cases with repeated consults were able to yield sensitive thresholds for outbreak detection.