Protection of the third-dose and fourth-dose mRNA vaccines against SARS-CoV-2 Omicron subvariant: a systematic review and meta-analysis

OBJECTIVES

The rapid spread of the SARS-CoV-2 Omicron variant has raised concerns regarding waning vaccine-induced immunity and durability. We evaluated protection of the third-dose and fourth-dose mRNA vaccines against SARS-CoV-2 Omicron subvariant and its sublineages.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Electronic databases and other resources (PubMed, Embase, CENTRAL, MEDLINE, CINAHL PLUS, APA PsycINFO, Web of Science, Scopus, ScienceDirect, MedRxiv and bioRxiv) were searched until December 2022.

STUDY ELIGIBILITY CRITERIA

We included studies that assessed the effectiveness of mRNA vaccine booster doses against SARS-CoV-2 infection and severe COVID-19 outcomes caused by the subvariant.

DATA EXTRACTION AND SYNTHESIS

Estimates of vaccine effectiveness (VE) at different time points after the third-dose and fourth-dose vaccination were extracted. Random-effects meta-analysis was used to compare VE of the third dose versus the primary series, no vaccination and the fourth dose at different time points. The certainty of the evidence was assessed by Grading of Recommendations, Assessments, Development and Evaluation approach.

RESULTS

This review included 50 studies. The third-dose VE, compared with the primary series, against SARS-CoV-2 infection was 48.86% (95% CI 44.90% to 52.82%, low certainty) at ≥14 days, and gradually decreased to 38.01% (95% CI 13.90% to 62.13%, very low certainty) at ≥90 days after the third-dose vaccination. The fourth-dose VE peaked at 14-30 days (56.70% (95% CI 50.36% to 63.04%), moderate certainty), then quickly declined at 61-90 days (22% (95% CI 6.40% to 37.60%), low certainty). Compared with no vaccination, the third-dose VE was 75.84% (95% CI 40.56% to 111.12%, low certainty) against BA.1 infection, and 70.41% (95% CI 49.94% to 90.88%, low certainty) against BA.2 infection at ≥7 days after the third-dose vaccination. The third-dose VE against hospitalisation remained stable over time and maintained 79.30% (95% CI 58.65% to 99.94%, moderate certainty) at 91-120 days. The fourth-dose VE up to 60 days was 67.54% (95% CI 59.76% to 75.33%, moderate certainty) for hospitalisation and 77.88% (95% CI 72.55% to 83.21%, moderate certainty) for death.

CONCLUSION

The boosters provided substantial protection against severe COVID-19 outcomes for at least 6 months, although the duration of protection remains uncertain, suggesting the need for a booster dose within 6 months of the third-dose or fourth-dose vaccination. However, the certainty of evidence in our VE estimates varied from very low to moderate, indicating significant heterogeneity among studies that should be considered when interpreting the findings for public health policies.

PROSPERO REGISTRATION NUMBER

CRD42023376698.

Protective effect of previous infection and vaccination against reinfection with BA.5 Omicron subvariant: a nationwide population-based study in Japan

Background

The Omicron variant of SARS-CoV-2 was reported to evade immunity derived from vaccination and previous infection. A better understanding of hybrid immunity informs effective infection control strategies. Since the reinfection risk was not well-assessed in East Asia, this study aims to evaluate the risk of infection with Omicron subvariant BA.5 among previously infected individuals in Japan.

Methods

All notified cases were extracted from the Japanese national COVID-19 surveillance database including 20,297,335 records up to 25 September 2022. Reinfection with BA.5 was defined as the infection notified during the BA.5 dominated period with any prior SARS-CoV-2 infection. The protective effect of prior infections against reinfections with BA.5 was estimated by applying a case-population design and the protective effect of vaccination was estimated by a multivariable Cox regression adjusting for age, sex, variants of prior infection, and the time since the last vaccination.

Findings

Among 19,830,548 SARS-CoV-2 first infections, 233,424 (1.2%) were reinfected with BA.5. The protective effect against BA.5 reinfection of prior infection with Wuhan strain was 46%, Alpha variant was 35%, Delta variant was 41%, and BA.1/BA.2 subvariant was 74%. The reduced risk of BA.5 reinfection by 7%, 33%, and 66% was associated with two, three, and four doses of vaccination, respectively, compared with one-dose vaccination.

Interpretation

The prior infections with Omicron subvariant BA.1/BA.2 protected BA.5 reinfection more than pre-Omicron variants. Increased frequency of vaccination led to more protection from reinfection with BA.5. Up-to-date vaccination may be encouraged to prevent future reinfection among the previously infected population.

Funding

None.

SARS-CoV-2 Variants and Age-Dependent Infection Rates among Household and Nonhousehold Contacts

To determine the effects of age and variants of concern on transmission of SARS-CoV-2, we analyzed infection rates among close contacts over 4 periods in Toyama Prefecture, Japan. Among household contacts, odds of infection were 6.2 times higher during the period of the Omicron variant than during previous periods, particularly among children and adolescents.

National seroepidemiological study of COVID-19 after the initial rollout of vaccines: Before and at the peak of the Omicron-dominant period in Japan

Background

Based on routine surveillance data, Japan has been affected much less by COVID-19 compared with other countries. To validate this, we aimed to estimate SARS-CoV-2 seroprevalence and examine sociodemographic factors associated with cumulative infection in Japan.

Methods

A population-based serial cross-sectional seroepidemiological investigation was conducted in five prefectures in December 2021 (pre-Omicron) and February-March 2022 (Omicron [BA.1/BA.2]-peak). Anti-nucleocapsid and anti-spike antibodies were measured to detect infection-induced and vaccine/infection-induced antibodies, respectively. Logistic regression was used to identify associations between various factors and past infection.

Results

Among 16 296 participants (median age: 53 [43-64] years), overall prevalence of infection-induced antibodies was 2.2% (95% CI: 1.9-2.5%) in December 2021 and 3.5% (95% CI: 3.1-3.9%) in February-March 2022. Factors associated with past infection included those residing in urban prefectures (Tokyo: aOR 3.37 [95% CI: 2.31-4.91], Osaka: aOR 3.23 [95% CI: 2.17-4.80]), older age groups (60s: aOR 0.47 [95% CI 0.29-0.74], 70s: aOR 0.41 [95% CI 0.24-0.70]), being vaccinated (twice: aOR 0.41 [95% CI: 0.28-0.61], three times: aOR 0.21 [95% CI: 0.12-0.36]), individuals engaged in occupations such as long-term care workers (aOR: 3.13 [95% CI: 1.47-6.66]), childcare workers (aOR: 3.63 [95% CI: 1.60-8.24]), food service workers (aOR: 3.09 [95% CI: 1.50-6.35]), and history of household contact (aOR: 26.4 [95% CI: 20.0-34.8]) or non-household contact (aOR: 5.21 [95% CI:3.80-7.14]) in February-March 2022. Almost all vaccinated individuals (15 670/15 681) acquired binding antibodies with higher titers among booster dose recipients.

Conclusions

Before Omicron, the cumulative burden was >10 times lower in Japan (2.2%) compared with the US (33%), the UK (25%), or global estimates (45%), but most developed antibodies owing to vaccination.

Comparison of Rhinovirus A-, B-, and C-Associated Respiratory Tract Illness Severity Based on the 5'-Untranslated Region Among Children Younger Than 5 Years

Background

Rhinoviruses (RVs) are among the most frequently detected viruses from hospitalized children with severe acute respiratory infections, being classified into RV-A, RV-B, and RV-C (4 clades: C, GAC1, GAC2, and A2). This study aimed to compare the clinical characteristics and respiratory tract illness severity between the RV species and RV-C clades in children in primary care and hospital settings in rural communities in the Philippines.

Methods

Clinical samples and information of children <5 years old in the Philippines were collected from 2014 to 2016. The samples were tested by reverse-transcription polymerase chain reaction (RT-PCR) targeting the 5′-untranslated region. PCR-positive samples were sequenced, and RV species were identified by phylogenetic analysis.

Results

Overall, 3680 respiratory tract illness episodes in 1688 cohort children were documented; 713 of those were RV positive and identified as RV-A (n = 271), RV-B (n = 47), and RV-C (n = 395: C [n = 76], GAG1 [n = 172], GAG2 [n = 8], A2 [n = 138], and unidentified [n = 1]). Severe illnesses, low oxygen saturation, cough, and wheezing were more common in patients with RV-C, especially with GAC1, than in those with RV-A or RV-B. Furthermore, severe illness was significantly more common in RV-C (GAC1)–positive cases than in RV-A–positive cases (odds ratio, 2.61 [95% CI, 1.17–4.13]).

Conclusions

Children infected with RV-C had more severe illnesses than children infected with RV-A and RV-B. Moreover, emerging clades of RV-C were associated with increased severity.

Impact of the Coming-of-Age Day and ceremony on the risk of SARS-CoV-2 transmission in Japan: A natural-experimental study based on national surveillance data

Background

Quantifying the impact on COVID‐19 transmission from a single event has been difficult due to the virus transmission dynamics, such as lag from exposure to reported infection, non‐linearity arising from the person‐to‐person transmission, and the modifying effects of non‐pharmaceutical interventions over time. To address these issues, we aimed to estimate the COVID‐19 transmission risk of social events focusing on the Japanese Coming‐of‐Age Day and Coming‐of‐Age ceremony in which “new adults” practice risky behavior on that particular day.

Methods

Using national surveillance data in Japan in 2021 and 2022, we conducted difference‐in‐differences regression against COVID‐19 incidences by setting “new adults” cases as the treatment group and the cases 1 year younger or older than these “new adults” as the control group. In addition, we employed a triple differences approach to estimate the risk of holding the Coming‐Age ceremony by using a binary variable regarding the presence or absence of the ceremony in each municipality.

Results

We estimated the relative risks (RRs) of the Coming‐of‐Age Day as 1.27 (95% confidence interval [CI] 1.02–1.57) in 2021 and 3.22 (95% CI 2.68–3.86) in 2022. The RR of the Coming‐of‐Age ceremony was also large, estimated as 2.83 (1.81–4.43) in 2022.

Conclusions

When planning large social events, it is important to be aware of the unique risks associated with these gatherings, along with effective public health messages to best communicate these risks.

Risk of Transmission and Viral Shedding From the Time of Infection for Respiratory Syncytial Virus in Households

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection worldwide, but reports of temporal changes in the risk of transmission among close contacts has been scarce. This study aimed to examine an association between the viral load trajectory and transmission risk to develop a better control strategy for the disease spread. We conducted a household-based prospective cohort study in Biliran Province, the Philippines, and enrolled 451 participants to observe the development of acute respiratory infection. Including the cases found at the health-care facility, we analyzed the data of viral loads with symptom records obtained from 172 followed participants who had household member positive for RSV with a rapid test during an RSV outbreak in 2018-2019. We developed a model estimating a temporal change in the viral shedding from the infection and evaluated transmission dynamics. We found that most transmission events occurred within approximately 7 days of the household exposure, including potential presymptomatic transmissions. The inferred risk of infection among those younger than 5 years was 3.5 times higher than that of those older than 5 years. This finding suggested that the initial week after the household exposure is particularly important for preventing RSV spread.

Epidemiological and clinical characteristics of children with acute respiratory viral infections in the Philippines: a prospective cohort study

OBJECTIVES

Viral acute respiratory infection (ARI) remains a major global health problem, especially among children in low- and middle-income countries. The study was conducted to reveal aetiological significance of respiratory viruses among both non-hospitalized and hospitalized children.

METHODS

A cohort study of children with ARI at the household, primary healthcare facility, and hospital levels was conducted alongside a hospital-based study including non-cohort children from 2014 to 2016 in the Philippines. The ARI cases were recorded at households and healthcare facilities, and a clinical investigation was performed. Nasopharyngeal swabs were collected from the symptomatic children and tested for respiratory viruses via polymerase chain reaction. Then, the association between healthcare facility utilization and viral detection was investigated.

RESULTS

Overall, 18,514 ARI cases were enrolled in the cohort study, and samples were collected from 4735 of these cases. The hospital-based study detected 648 ARI cases, all of which were sampled. Rhinovirus (22.2%; 1052/4735) was most frequently detected followed by respiratory syncytial virus (12.0%; 566/4735). Enterovirus (adjusted odds ratio, 1.8; 95% confidence interval, 1.1-2.8), human metapneumovirus (2.1, 1.4-3.2), rhinovirus (2.1, 1.8-2.6), and respiratory syncytial virus (1.6, 1.2-1.9) were significantly more prevalent in the ARI cases at healthcare facilities than in those in households. Of all ARI cases, 0.6% required hospitalization while 1.8% were hospitalized among the respiratory syncytial virus-positive cases (3.8, 3.0-4.9).

CONCLUSIONS

We determined the prevalence of respiratory viruses among children with ARIs at the household, primary healthcare facility, and hospital levels and the association with clinical characteristics. In particular, we discovered a significant disease burden and impact of respiratory syncytial virus infections as well as a considerable aetiological implication of rhinovirus infections.

Use of antibiotics for common illnesses among children aged under 5 years in a rural community in Indonesia: a cross-sectional study

Background

The incidence of antimicrobial resistance has been increasing worldwide in the past decades, which includes resistance to bacteria that cause common childhood illnesses, such as acute respiratory infections and diarrhea. Numerous children with those common illnesses are treated with antibiotics. However, in such cases, antibiotic treatment is not required. Community-based studies focusing on antibiotic use among children are still limited. This study aimed to identify the prevalence of antibiotic use for common childhood illnesses and to investigate factors associated with antibiotic use in children under 5 years old as well as female caregivers in a rural community in Indonesia.

Methods

A cross-sectional study of 334 children in three villages of Banten Province, located in the western part of Java Island, was conducted in May 2018. Female caregivers who were responsible for providing medications to children were interviewed. We obtained information such as demographic data, any common clinical illness within the last 30 days, and antibiotic usage during an episode of illness. We excluded children with underlying disease that require a regular follow-up and children who were hospitalized in the last 30 days in the analysis. Antibiotic use answered by female caregivers was verified by checking its package or showing photos of various antibiotics to the female caregivers. Crushed antibiotics were confirmed with health professionals.

Results

A total of 203 children had clinical symptoms, and the most common symptom was fever and respiratory symptoms. In total, 49.3% received antibiotics, and 66% of them were prescribed by private health professionals. Only two children received antibiotics without a prescription. The most common antibiotic used among children was amoxicillin.

Conclusions

The high prevalence of antibiotic use was observed in children under 5 years of age, and the major source to obtain antibiotics was to consult health professionals. Training on appropriate antibiotic use must be conducted for health professionals in not only public but also private sectors.

An enterohaemorrhagic Escherichia coli outbreak spread through the environment at an institute for people with intellectual disabilities in Japan in 2005

OBJECTIVE

An enterohaemorrhagic Escherichia coli (EHEC) outbreak at an institute with multiple facilities for children and adults with intellectual disabilities was investigated to characterize the cases and identify risk factors for infection.

METHODS

A case was defined as a resident, a staff member or a visitor at the institute from 16 May through 30 June 2005 testing positive for type 2 Vero toxin-producing EHEC O157:H7 (confirmed case) or exhibiting bloody diarrhoea for two or more days (probable case). We collected and analysed demographic, clinical, laboratory and individual behaviour data to identify possible risk factors for infection and infection routes.

RESULTS

We recorded 58 confirmed cases, of which 13 were symptomatic. One probable case was also found. The median age of the patients was 37 years (range: 6-59 years). Thirty-six patients (61%) were male. Thirteen patients (93%) had diarrhoea and six (43%) had abdominal pain. Two developed haemolytic-uraemic syndrome but recovered. All the patients were treated with antibiotics and tested negative after treatment. Some residents had problems with personal hygiene. The residents of one of the facilities who cleaned a particular restroom had 18.0 times higher odds of being infected with EHEC (95% confidence interval: 4.0-102.4) than those who did not.

DISCUSSION

The source of the outbreak could not be identified; however, the infection may have spread through environmental sources contaminated with EHEC. We recommend that institutional settings, particularly those that accommodate people with intellectual disabilities, clean restrooms as often as possible to reduce possible infection from contact with infected surfaces.

Aetiology and risks factors associated with the fatal outcomes of childhood pneumonia among hospitalised children in the Philippines from 2008 to 2016: a case series study

OBJECTIVE

Pneumonia remains the leading cause of hospitalisations and deaths among children aged <5 years. Diverse respiratory pathogens cause acute respiratory infections, including pneumonia. Here, we analysed viral and bacterial pathogens and risk factors associated with death of hospitalised children.

DESIGN

A 9-year case series study.

SETTING

Two secondary-care hospitals, one tertiary-care hospital and one research centre in the Philippines.

PARTICIPANTS

5054 children aged <5 years hospitalised with severe pneumonia.

METHODS

Nasopharyngeal swabs for virus identification, and venous blood samples for bacterial culture were collected. Demographic, clinical data and laboratory findings were collected at admission time. Logistic regression analyses were performed to identify the factors associated with death.

RESULTS

Of the enrolled patients, 57% (2876/5054) were males. The case fatality rate was 4.7% (238/5054), showing a decreasing trend during the study period (p<0.001). 55.0% of the patients who died were either moderately or severely underweight. Viruses were detected in 61.0% of the patients, with respiratory syncytial virus (27.0%) and rhinovirus (23.0%) being the most commonly detected viruses. In children aged 2-59 months, the risk factors significantly associated with death included age of 2-5 months, sensorial changes, severe malnutrition, grunting, central cyanosis, decreased breath sounds, tachypnoea, fever (≥38.5°C), saturation of peripheral oxygen <90%, infiltration, consolidation and pleural effusion on chest radiograph.Among the pathogens, adenovirus type 7, seasonal influenza A (H1N1) and positive blood culture for bacteria were significantly associated with death. Similar patterns were observed between the death cases and the aforementioned factors in children aged <2 months.

CONCLUSION

Malnutrition was the most common factor associated with death and addressing this issue may decrease the case fatality rate. In addition, chest radiographic examination and oxygen saturation measurement should be promoted in all hospitalised patients with pneumonia as well as bacteria detection to identify patients who are at risk of death.

Age-specific incidence rates and risk factors for respiratory syncytial virus-associated lower respiratory tract illness in cohort children under 5 years old in the Philippines

Background

Respiratory syncytial virus (RSV) is one of the main viral causes of lower respiratory tract illness (LRTI), especially in young children. RSV vaccines, including maternal and infant vaccines, are under development; however, more epidemiological studies are needed to develop effective vaccination strategies.

Objectives

To estimate detailed age‐specific incidence rates and severity of RSV‐associated LRTI (RSV‐LRTI) using data from a community‐based prospective cohort study in the Philippines.

Patients/Methods

Cohort children who visited health facilities due to acute respiratory symptoms were identified, and nasopharyngeal swabs were collected to detect RSV. The severity of RSV‐LRTI was assessed using the severity definition proposed by the World Health Organization. Risk factors for developing RSV‐LRTI and contribution of SpO₂ measurement were also evaluated.

Results

A total of 395 RSV episodes which occurred in children aged 2‐59 months were categorised as 183 RSV‐LRTI, 72 as severe RSV‐LRTI and 29 as very severe RSV‐LRTI. Children aged 3‐5 months had the highest incidence rate of RSV‐LRTI, at 207.4 per 1000 child‐years (95% CI: 149.0‐279.5). Younger age group, place of living and low educational level of caregivers were associated with developing RSV‐LRTI. Clinical manifestations had low levels of agreement with hypoxaemia as measured by pulse oximeter.

Conclusion

The highest burden of RSV was observed in young infants aged 3‐5 months, whereas the burden was also high in those aged 12‐20 months. Future vaccination strategies should consider the protection of older children, especially those aged one year, as well as young infants.

Transmission of Respiratory Syncytial Virus Among Children Under 5 Years in Households of Rural Communities, the Philippines

Background

To develop a more effective vaccination strategy for reducing the impact of respiratory syncytial virus (RSV) infection, especially in young infants (<6 months old), it is necessary to understand the transmission dynamics of RSV.

Methods

We conducted a community-based prospective cohort study from 2014 to 2016 in Biliran Province, the Philippines, on children <5 years old. We collected nasopharyngeal swabs from symptomatic children with acute respiratory infection (ARI) during household visits and at health facilities. In households (n = 181) with RSV-positive ARI cases (RSV-ARI), we also identified ARI episodes among other children <5 years old in the same household. In addition, we determined the serial interval to estimate the basic reproduction number (R₀), the average number of secondary cases generated by a single primary case.

Results

In the 181 households analyzed, we found 212 RSV-ARI in 152 households with a single case and 29 households with multiple cases, which included 29 1st RSV-ARI and 31 2nd RSV-ARI. We also found possible index cases among children <5 years old in the same household for 29.0% (18 of 62) of young infants with RSV-ARI. The estimated mean serial interval was 3.2 days, and R₀ was estimated to be 0.92–1.33 for RSV-A and 1.04–1.76 for RSV-B, which varied between different times (2014 and 2015) and places.

Conclusions

Young infants are likely to acquire RSV infection from older children in the same household. Therefore, vaccination targeting older children might protect infants from RSV infection.

Extensive first-principles molecular dynamics study on Li encapsulation into C60 and its experimental confirmation

The aim of increasing the production ratio of endohedral C₆₀ by impinging foreign atoms against C₆₀ is a crucial matter of the science and technology employed towards industrialization of these functional building block materials. Among these endohedral fullerenes, Li⁺@C₆₀ exhibits a wide variety of physical and chemical phenomena and has the potential to be applicable in areas spanning the medical field to photovoltaics. However, currently, Li⁺@C₆₀ can be experimentally produced with only ∼1% ratio using the plasma shower method with a 30 eV kinetic energy provided to the impinging Li⁺ ion. From extensive first-principles molecular dynamics simulations, it is found that the maximum production ratio of Li⁺@C₆₀ per hit is increased to about 5.1% (5.3%) when a Li⁺ ion impinges vertically on a six-membered ring of C₆₀ with 30 eV (40 eV) kinetic energy, although many C₆₀ molecules are damaged during this collision. On the contrary, when it impinges vertically on a six-membered ring with 10 eV kinetic energy, the production ratio remains at 1.3%, but the C₆₀ molecules are not damaged at all. On the other hand, when the C₆₀ is randomly oriented, the production ratio reduces to about 3.7 ± 0.5%, 3.3 ± 0.5%, and 0.2 ± 0.03% for 30 eV, 40 eV, and 10 eV kinetic energy, respectively. Based on these observations we demonstrate the possibility of increasing the production ratio by fixing six-membered rings atop C₆₀ using the Cu(111) substrate or UV light irradiation. In order to assess the ideal experimental production ratio, the ⁷Li solid NMR spectroscopy measurement is also performed for the multilayer randomly oriented C₆₀ sample irradiated by Li⁺ using the plasma shower method combined with inductively coupled plasma atomic emission spectroscopy (ICP-AES). Time-of-flight mass spectroscopy measurements are also performed to cross check whether Li⁺@C₆₀ molecules are produced in the sample. The resulting experimental estimate, 4% for 30 eV incident kinetic energy, fully agrees with our simulation results mentioned above, suggesting the consistency and accuracy of our simulations and experiments.

Estimates of influenza and respiratory syncytial virus incidences with fraction modeling approach in Baguio City, the Philippines, 2012-2014

BACKGROUND

Estimation of the incidences of influenza and respiratory syncytial virus (RSV) infection is important for disease control. Previous estimate in the city showed a substantial burden of influenza in both outpatients and inpatients while it did not account for individuals who do not seek medical attention nor RSV.

PATIENTS/METHODS

A total of 17 674 influenza-like illness (ILI) and 13 242 severe acute respiratory illness (SARI) cases were recruited, and samples were collected from 6267 and 2962 of ILI and SARI cases, respectively. RT-PCR assays were performed to detect influenza and RSV in the samples. A health-seeking behavior survey was conducted from February 2014 to April 2014 to estimate the fraction of infected individuals who did not seek medical attention between rainy and dry season.

RESULTS

Average influenza and RSV incidence rates in outpatients were 1.6 and 1.4 per 1000 individuals, respectively, and the highest incidence rate for both viruses was found in the of 6-23 month age group. Average influenza and RSV hospitalization incidence rates were 1.7 and 1.9 per 1000 individuals, respectively. Further, we estimated that the incidence rates of influenza and RSV in individuals who did not seek medical attention were threefold and 1.6-fold those in the medically attended population.

CONCLUSIONS

Respiratory syncytial virus and influenza pose a substantial disease burden, particularly in hospitalized cases. The implementation of either a community-based approach or an enhanced surveillance system in combination with a community survey will allow a better understanding of the disease burdens of RSV and influenza in the Philippines.

Seasonality of Influenza and Respiratory Syncytial Viruses and the Effect of Climate Factors in Subtropical-Tropical Asia Using Influenza-Like Illness Surveillance Data, 2010 -2012

INTRODUCTION

The seasonality of influenza and respiratory syncytial virus (RSV) is well known, and many analyses have been conducted in temperate countries; however, this is still not well understood in tropical countries. Previous studies suggest that climate factors are involved in the seasonality of these viruses. However, the extent of the effect of each climate variable is yet to be defined.

MATERIALS AND METHODS

We investigated the pattern of seasonality and the effect of climate variables on influenza and RSV at three sites of different latitudes: the Eastern Visayas region and Baguio City in the Philippines, and Okinawa Prefecture in Japan. Wavelet analysis and the dynamic linear regression model were applied. Climate variables used in the analysis included mean temperature, relative and specific humidity, precipitation, and number of rainy days. The Akaike Information Criterion estimated in each model was used to test the improvement of fit in comparison with the baseline model.

RESULTS

At all three study sites, annual seasonal peaks were observed in influenza A and RSV; peaks were unclear for influenza B. Ranges of climate variables at the two Philippine sites were narrower and mean variables were significantly different among the three sites. Whereas all climate variables except the number of rainy days improved model fit to the local trend model, their contributions were modest. Mean temperature and specific humidity were positively associated with influenza and RSV at the Philippine sites and negatively associated with influenza A in Okinawa. Precipitation also improved model fit for influenza and RSV at both Philippine sites, except for the influenza A model in the Eastern Visayas.

CONCLUSIONS

Annual seasonal peaks were observed for influenza A and RSV but were less clear for influenza B at all three study sites. Including additional data from subsequent more years would help to ascertain these findings. Annual amplitude and variation in climate variables are more important than their absolute values for determining their effect on the seasonality of influenza and RSV.

[Response to Ebola Virus Disease Outbreak: Experience in Field Epidemiology in Sierra Leone]

The Ebola virus disease (EVD) outbreak that occurred in West Africa in 2014 was the largest ever in the world. In Sierra Leone, the number of cases reported peaked in December 2014 and gradually declined. However, the outbreak was not immediately terminated. To support the response of the World Health Organization (WHO) to EVD, the WHO Western Pacific Regional Office established the Western Pacific Ebola Support Team (WEST) with the aim of eliminating EVD in Port Loko District, where a certain number of new cases were still being reported in March 2015. We were dispatched to join WEST as WHO short term consultants in epidemiology for about six weeks from March to June 2015. Here, we describe our activities in the field as epidemiologists to show how Japan can contribute in the area of epidemiology during infectious disease outbreaks of international concern. The analysis suggested that the surveillance data for all the deaths and suspected EVD cases were underreporting the actual number of EVD cases in Port Loko District. Although contact tracing was conducted, new EVD cases were often found among untraced contacts because of inadequate information from residents or insufficient investigation by the contact tracing team. In addition, incomplete monitoring of the health status of close contacts resulted in secondary transmission of the disease. Data managers established a database by centralizing data from the surveillance and contact tracing teams, laboratories, and healthcare facilities. The number of deaths per week recorded by these data sources was lower than the number of deaths per week that would be expected from the national mortality statistics. The team strengthened surveillance and social mobilization in the regions with wide disparities between the actual and reported numbers of deaths. For the on-the-ground activities, the field coordinator, epidemiologists, and social mobilizers, as well as the logistic and administrative support personnel, were all indispensable in supporting the field investigation of these infectious disease outbreaks of public health concern. A field coordinator, in particular, requires outstanding knowledge, experience and skills to lead team operations in liaison with international and local partners and to build confidence among local residents. The development of these human resources and the maintenance of a response team are required for potential future outbreaks, and this is an important area that Japan could prepare for and then contribute to future outbreaks. This report does not represent an official view of the WHO or our affiliates.

Local persistence and global dissemination play a significant role in the circulation of influenza B viruses in Leyte Island, Philippines

The local and global transmission dynamics of influenza B virus is not completely understood mainly because of limited epidemiological and sequence data for influenza B virus. Here we report epidemiological and molecular characteristics of influenza B viruses from 2010 to 2013 in Leyte Island, Philippines. Phylogenetic analyses showed global dissemination of the virus among both neighboring and distant areas. The analyses also suggest that southeast Asia is not a distributor of influenza B virus and can introduce the virus from other areas. Furthermore, we found evidence on the local persistence of the virus over years in the Philippines. Taken together, both local persistence and global dissemination play a significant role in the circulation of influenza B virus.

Burden of Influenza and Respiratory Syncytial Virus Infection in Pregnant Women and Infants Under 6 Months in Mongolia: A Prospective Cohort Study

Background

Pregnant women and infants under 6 months are at risk of influenza-related complications. Limited information exists on their community burden of respiratory viruses.

Methods and Findings

This prospective, observational open cohort study was conducted in Baganuur district, Ulaanbaatar, Mongolia during 2013/14 and 2014/15 influenza seasons. Influenza-like illness (ILI) and severe acute respiratory infection (sARI) were identified by follow-up calls twice a week. For those identified, influenza and respiratory syncytical virus (RSV) were tested by point-of-care test kits. We calculated overall and stratified (by trimester or age group) incidence rates (IR) and used Cox proportional hazard regression for risk factor analyses. Among 1260 unvaccinated pregnant women enrolled, overall IRs for ILI, sARI and influenza A were 11.8 (95% confidence interval (C.I):11.2–12.4), 0.1 (95%C.I:0.0–0.4), and 1.7 (95%C.I:1.5–1.9) per 1,000person-days, respectively. One sARI case was influenza A positive. IRs and adjusted hazard ratios (Adj.HR) for ILI and influenza A were lowest in the third trimester. Those with co-morbidity were 1.4 times more likely to develop ILI [Adj.HR:1.4 (95%C.I:1.1–1.9)]. Among 1304 infants enrolled, overall ILI and sARI IRs were 15.2 (95%C.I:14.5–15.8) and 20.5 (95%C.I:19.7–21.3) per 1,000person-days, respectively. From the tested ILI (77.6%) and sARI (30.6%) cases, the overall positivity rates were 6.3% (influenza A), 1.1% (influenza B) and 9.3% (RSV). Positivity rates of influenza A and RSV tend to increase with age. sARI cases were 1.4 times more likely to be male [Adj.HR:1.4 (95%C.I:1.1–1.8)]. Among all influenza A and RSV positive infants, 11.8% and 68.0% were respectively identified among sARI hospitalized cases.

Conclusion

We observed low overall influenza A burden in both groups, though underestimation was likely due to point-of-care tests used. For infants, RSV burden was more significant than influenza A. These findings would be useful for establishing control strategies for both viruses in Mongolia.

Molecular and mathematical modeling analyses of inter-island transmission of rabies into a previously rabies-free island in the Philippines

Rabies is endemic in the Philippines and dog bites are a major cause of rabies cases in humans. The rabies control program has not been successful in eliminating rabies because of low vaccination coverage among dogs. Therefore, more effective and feasible strategies for rabies control are urgently required in the country. To control rabies, it is very important to know if inter-island transmission can occur because rabies can become endemic once the virus is introduced in areas that previously had no reported cases. Our molecular epidemiological study suggests that inter-island transmission events can occur; therefore, we further investigated these inter-island transmission using phylogenetic and modeling approaches. We investigate inter-island transmission between Luzon and Tablas Islands in the Philippines. Phylogenetic analysis and mathematical modeling demonstrate that there was a time lag of several months to a year from rabies introduction to initial case detection, indicating the difficulties in recognizing the initial rabies introductory event. There had been no rabies cases reported in Tablas Island; however, transmission chain was sustained on this island after the introduction of rabies virus because of low vaccination coverage among dogs. Across the islands, a rabies control program should include control of inter-island dog transportation and rabies vaccination to avoid viral introduction from the outside and to break transmission chains after viral introduction. However, this program has not yet been completely implemented and transmission chains following inter-island virus transmission are still observed. Local government units try to control dog transport; however, it should be more strictly controlled, and a continuous rabies control program should be implemented to prevent rabies spread even in rabies-free areas.

SOCIO-DEMOGRAPHIC CHARACTERISTICS AND GEOGRAPHIC DISTRIBUTION OF REPORTED MALARIA CASES IN BANGKA DISTRICT, BABEL ISLAND PROVINCE, INDONESIA DURING 2008-2012

Malaria is a major health problem in many developing countries including Indonesia. The purpose of this study was to investigate the socio-demographic characteristics and geographic distribution of malaria cases in Bangka District, Bangka-Belitung Island Province, Indonesia. Bangka District is a malaria endemic area of Indonesia. We analyzed the epidemiological data of all reported malaria cases during 2008-2012 in Bangka District. Of the 4,756 malaria-confirmed cases reported during the study period, 3,234 (68. 0%) were among persons aged ≥ 15 years, 1,024 (21.5%) were among persons aged 5-14 years and 498 (10.5%) were among persons aged < 5 years. Malaria cases were primarily located along the sea coast and less frequently in inland. Malaria cases were found not only among the local population but also among migrant workers. The monthly incidence of reported malaria cases in the study population ranged from 0.06 to 1.06 per 1,000 person-months. The cases were mostly due to Plasmodium vivax (57.1%) followed by Plasmodiumfalciparum (40.2%). Plasmodiumfalciparum was more common among migrant workers while Plasmodium vivax was more common among the local population (Odds ratio 1.2; p = 0.03). The main transmission vector found in the coastal area was Anopheles sundaicus. An. letifer and An. barbirostris were found inland. We identified "malaria hot-spots" in the study area using a Geographic Information System. The results of this study will contribute to the malaria control program.

Analysis of influenza transmission in the households of primary and junior high school students during the 2012-13 influenza season in Odate, Japan

BACKGROUND

Households are one of the major settings of influenza transmission in the community and transmission is frequently initiated by school-aged children. We surveyed households with primary school (PS) and/ or junior high school (JH) children for the 2012-13 influenza season in Odate, Japan then characterized the epidemiology of influenza household transmission as well as estimated the serial intervals.

METHODS

We delivered a self-reported questionnaire survey to households with PS and/or JH school children in Odate City, Japan. Influenza A (H3N2) virus predominantly circulated during the 2012-13 influenza season. We investigated the epidemiological characteristics of within-household transmission and calculated the serial intervals (SI). SIs were drew by a non-parametric model and compared with parametric models by the Akaike Information Criterion. The covariable contributions were investigated by the accelerated failure model.

RESULTS

Household influenza transmission was identified in 255 out of 363 household respondents. Primary school (PS) children accounted for 45.1 % of primary cases, and disease transmission was most commonly observed between PS children and parents, followed by transmission from PS children to siblings. In primary cases of PS or JH children, younger age and longer absence from school were significantly associated with household transmission events. The mean SI was estimated as 2.8 days (95 % confidence interval 2.6-3.0 days) in the lognormal model. The estimated acceleration factors revealed that while secondary school age and the absence duration > 7 days were associated with shorter and longer SIs, respectively, antiviral prescriptions for primary cases made no contribution.

CONCLUSIONS

High frequencies of household transmission from primary school with shorter SI were found. These findings contribute to the development of future mitigation strategies against influenza transmission in Japan.

Role of Preschool and Primary School Children in Epidemics of Influenza A in a Local Community in Japan during Two Consecutive Seasons with A(H3N2) as a Predominant Subtype

Enhanced influenza surveillance was implemented to analyze transmission dynamics particularly driving force of influenza transmission in a community during 2011/12 and 2012/13 seasons in Odate City, Japan. In these two consecutive seasons, influenza A(H3N2) was the predominant influenza A subtype. Suspected influenza cases were tested by commercial rapid test kits. Demographic and epidemiological information of influenza positive cases were recorded using a standardized questionnaire, which included age or age group, date of visit, date of fever onset, and the result of rapid test kit. Epidemiological parameters including epidemic midpoint (EM) and growth rate (GR) were analyzed. In 2012/13 season, numbers of influenza A positive cases were significantly lower among preschool (212 cases) and primary school (224 cases) children than in 2011/12 season (461 and 538 cases, respectively). Simultaneously, total influenza A cases were also reduced from 2,092 in 2011/12 season to 1,846 in 2012/13 season. The EMs in preschool and primary school children were earlier than EMs for adult and all age group in both 2011/12 and 2012/13 seasons. The GR in 2012/13 season was significantly lower than that in 2011/12 season (0.11 and 0.18, respectively, p = 0.003). Multiple linear regression analysis by school districts revealed that GRs in both seasons were significantly correlated with the incidence of school age children. Our findings suggest that preschool and primary school children played an important role as a driving force of epidemics in the community in both 2011/12 and 2012/13 seasons. The reduction of total influenza A cases in 2012/13 season can be explained by decreased susceptible population in these age groups due to immunity acquired by infections in 2011/12 season. Further investigations are needed to investigate the effect of pre-existing immunity on influenza transmission in the community.

Incidence and Risk Factors of Childhood Pneumonia-Like Episodes in Biliran Island, Philippines--A Community-Based Study

Pneumonia is a leading cause of deaths in infants and young children in developing countries, including the Philippines. However, data at the community level remains limited. Our study aimed to estimate incidence and mortality rates and to evaluate risk factors and health-seeking behavior for childhood pneumonia. A household level interview survey was conducted in Biliran Island, the Philippines. Caregivers were interviewed using a semi-structured questionnaire to check if children had symptoms suggesting pneumonia-like episodes from June 2011 to May 2012. Of 3,327 households visited in total, 3,302 (99.2%) agreed to participate, and 5,249 children less than 5 years of age were included in the study. Incidence rates of pneumonia-like episodes, severe pneumonia-like episodes, and pneumonia-associated mortality were 105, 61, and 0.9 per 1,000 person-years, respectively. History of asthma [hazard ratio (HR): 5.85, 95% confidence interval (CI): 4.83–7.08], low socioeconomic status (SES) (HR: 1.11, 95% CI: 1.02–1.20), and long travel time to the healthcare facility estimated by cost distance analysis (HR: 1.32, 95% CI: 1.09–1.61) were significantly associated with the occurrence of pneumonia-like episodes by the Cox proportional hazards model. For severe pneumonia-like episodes, a history of asthma (HR: 8.39, 95% CI: 6.54–10.77) and low SES (HR: 1.30, 95% CI: 1.17–1.45) were significant risk factors. Children who had a long travel time to the hospital were less likely to seek hospital care (Odds ratio: 0.32, 95% CI: 0.19–0.54) when they experienced severe pneumonia-like episodes. Incidence of pediatric pneumonia-like episodes was associated with a history of asthma, SES, and the travel time to healthcare facilities. Travel time was also identified as a strong indicator for health-seeking behavior. Improved access to healthcare facilities is important for early and effective management. Further studies are warranted to understand the causal relationship between asthma and pneumonia.

Influenza and other respiratory viruses detected by influenza-like illness surveillance in Leyte Island, the Philippines, 2010-2013

This study aimed to determine the role of influenza-like illness (ILI) surveillance conducted on Leyte Island, the Philippines, including involvement of other respiratory viruses, from 2010 to 2013. ILI surveillance was conducted from January 2010 to March 2013 with 3 sentinel sites located in Tacloban city, Palo and Tanauan of Leyte Island. ILI was defined as fever ≥38°C or feverish feeling and either cough or running nose in a patient of any age. Influenza virus and other 5 respiratory viruses were searched. A total of 5,550 ILI cases visited the 3 sites and specimens were collected from 2,031 (36.6%) cases. Among the cases sampled, 1,637 (75.6%) were children aged <5 years. 874 (43.0%) cases were positive for at least one of the respiratory viruses tested. Influenza virus and respiratory syncytial virus (RSV) were predominantly detected (both were 25.7%) followed by human rhinovirus (HRV) (17.5%). The age distributions were significantly different between those who were positive for influenza, HRV, and RSV. ILI cases were reported throughout the year and influenza virus was co-detected with those viruses on approximately half of the weeks of study period (RSV in 60.5% and HRV 47.4%). In terms of clinical manifestations, only the rates of headache and sore throat were significantly higher in influenza positive cases than cases positive to other viruses. In conclusion, syndromic ILI surveillance in this area is difficult to detect the start of influenza epidemic without laboratory confirmation which requires huge resources. Age was an important factor that affected positive rates of influenza and other respiratory viruses. Involvement of older age children may be useful to detect influenza more effectively.

Epidemiology and impact of influenza in Mongolia, 2007-2012

Background

Mongolia's Health Service began to conduct surveillance for influenza in the 1970s. This surveillance has become more comprehensive over time and now includes 155 sentinel sites in Mongolia. In this study, we analyzed the epidemiological characteristics and impact of influenza using data from influenza surveillance in Mongolia.

Materials and methods

The data were collected by the National Influenza Center, Mongolia (NIC). Incidence rates of influenza-like illness (ILI) and severe acute respiratory infections (sARI) were calculated as the proportion of the number of ILI and sARI cases to the total population in the studied areas. Nasopharyngeal samples were collected and tested using real-time reverse transcription polymerase chain reaction [(rt)-RT-PCR]. Selected samples negative for influenza were tested for other respiratory pathogens by multiplex rt-RT-PCR.

Results

Averages of 14·0 ILI and 0·8 sARI episodes per 100 population per year were observed during the five influenza seasons. The highest incidences of influenza associated with ILI and sARI were observed among children 0–4 years old. The number of ILI cases showed a clear seasonality, generally peaking between December and February. In contrast, sARI incidence peaked twice during each season. Influenza B was most prevalent during 2007–2008 and 2011–2012, influenza A (H3N2) during 2010–2011, seasonal A (H1N1) during 2008–2009, and A (H1N1) pdm09 during 2009–2010.

Conclusions

Additional data on the epidemiology and impact of influenza including socioeconomic impact and vaccine effectiveness are required to develop a national influenza control policy, including a vaccination strategy. Our results provide useful data for developing such a policy.

Analysis of medical consultation interval between the symptom onset and consultation observed in multiple medical facilities in Odate city, Japan, 2011/2012 and 2012/2013 seasons

BACKGROUND

Influenza remains one of the most important causes of respiratory infection despite the widespread availability of vaccines. Anti-influenza viral agents such as neuraminidase inhibitors are generally efficacious in alleviating the symptoms if they are administered within 2 days of the illness onset. However, few studies have examined the situation of interval between illness onset and medical consultation in influenza outpatients on community level. And the predictors or determinants for longer medical consultation interval have not been well-defined.

MATERIAL AND METHOD

An enhanced surveillance study was conducted in Odate city of Japan in 2 consecutive seasons from 2011 to 2013. The late consultation rate (>2 days) and its risk factors were investigated in confirmed influenza outpatients.

RESULTS

A proportion of 5.5% of patients visited doctors beyond 2 days of illness onset. Illness onset during non-high-incidence period, infection with influenza B and being adult or elderly were identified as independent risk factors for late consultation and the risk increased with the number of risk factors.

CONCLUSION

The consultation behavior for influenza was generally well in our study population. Identified risk factors should be addressed in health education and promotion for the late consultation.

Phylogeographic analysis of rabies viruses in the Philippines

Rabies still remains a public health threat in the Philippines. A significant number of human rabies cases, about 200-300 cases annually, have been reported, and the country needs an effective strategy for rabies control. To develop an effective control strategy, it is important to understand the transmission patterns of the rabies viruses. We conducted phylogenetic analyses by considering the temporal and spatial evolution of rabies viruses to reveal the transmission dynamics in the Philippines. After evaluating the molecular clock and phylogeographic analysis, we estimated that the Philippine strains were introduced from China around the beginning of 20th century. Upon this introduction, the rabies viruses evolved within the Philippines to form three major clades, and there was no indication of introduction of other rabies viruses from any other country. However, within the Philippines, island-to-island migrations were observed. Since then, the rabies viruses have diffused and only evolved within each island group. The evolutionary pattern of these viruses was strongly shaped by geographical boundaries. The association index statistics demonstrated a strong spatial structure within the island group, indicating that the seas were a significant geographical barrier for viral dispersal. Strong spatial structure was also observed even at a regional level, and most of the viral migrations (79.7% of the total median number) in Luzon were observed between neighboring regions. Rabies viruses were genetically clustered at a regional level, and this strong spatial structure suggests a geographical clustering of transmission chains and the potential effectiveness of rabies control that targets geographical clustering. Dog vaccination campaigns have been conducted independently by local governments in the Philippines, but it could be more effective to implement a coordinated vaccination campaign among neighboring areas to eliminate geographically-clustered rabies transmission chains.

Investigation of an Influenza A (H3N2) outbreak in evacuation centres following the Great East Japan earthquake, 2011

Background

The Great East Japan Earthquake of magnitude 9.0 that struck on 11 March 2011 resulted in more than 18000 deaths or cases of missing persons. The large-scale tsunami that followed the earthquake devastated many coastal areas of the Tohoku region, including Miyagi Prefecture, and many residents of the tsunami-affected areas were compelled to reside in evacuation centres (ECs). In Japan, seasonal influenza epidemics usually occur between December and March. At the time of the Great East Japan Earthquake on 11 March 2011, influenza A (H3N2) was still circulating and there was a heightened concern regarding severe outbreaks due to influenza A (H3N2).

Methods

After local hospital staff and public health nurses detected influenza cases among the evacuees, an outbreak investigation was conducted in five ECs that had reported at least one influenza case from 23 March to 11 April 2011. Cases were confirmed by point-of-care tests and those residues were obtained and subjected to reverse transcription PCR and/or real time RT-PCR for sub-typing of influenza.

Results

There were 105 confirmed cases detected during the study period with a mean attack rate of 5.3% (range, 0.8%–11.1%). An epidemiological tree for two ECs demonstrated same-room and familial links that accounted for 88.5% of cases. The majority of cases occurred in those aged 15-64 years, who were likely to have engaged in search and rescue activities. No deaths were reported in this outbreak. Familial link accounted for on average 40.5% of influenza cases in two ECs and rooms where two or more cases were reported accounted for on average 85% in those ECs. A combination of preventative measures, including case cohorting, personal hygiene, wearing masks, and early detection and treatment, were implemented during the outbreak period.

Conclusions

Influenza can cause outbreaks in a disaster setting when the disaster occurs during an epidemic influenza season. The transmission route is more likely to be associated with sharing room and space and with familial links. The importance of influenza surveillance and early treatments should be emphasized in EC settings for implementing preventive control measures.

Estimating influenza outpatients' and inpatients' incidences from 2009 to 2011 in a tropical urban setting in the Philippines

Objectives

Although the public health significance of influenza in regions with a temperate climate has been widely recognized, information on influenza burden in tropical countries, including the Philippines, remains limited. We aimed to estimate influenza incidence rates for both outpatients and inpatients then characterized their demographic features.

Design

An enhanced surveillance was performed from January 2009 to December 2011 in an urbanized highland city. The influenza-like illness (ILI) surveillance involved all city health centers and an outpatient department of a tertiary government hospital. The severe acute respiratory infection (sARI) surveillance was also conducted with one government and four private hospitals since April 2009. Nasal and/or oropharyngeal swabs were collected and tested for influenza A, influenza B, and respiratory syncytial virus.

Results and Conclusions

We obtained 5915 specimens from 13 002 ILI cases and 2656 specimens from 10 726 sARI cases throughout the study period. We observed year-round influenza activity with two possible peaks each year. The overall influenza detection rate was 23% in the ILI surveillance and 9% in the sARI surveillance. The mean annual outpatient incidence rate of influenza was 5·4 per 1000 individuals [95% confidence interval (CI), 1·83–12·7], and the mean annual incidence of influenza-associated sARI was 1·0 per 1000 individuals (95% CI, 0·03–5·57). The highest incidence rates were observed among children aged <5 years, particularly those aged 6–23 months. Influenza posed a certain disease burden among inpatients and outpatients, particularly children aged <5 years, in an urbanized tropical city of the Philippines.

Epidemiological characterization of influenza A(H1N1)pdm09 cases from 2009 to 2010 in Baguio City, the Philippines

Background

Baguio City, Philippines experienced its first influenza A(H1N1)pdm09 [A(H1)pdm09] case in May 2009. In spite of numerous reports describing the epidemiological and clinical features of A(H1)pdm09 cases, there are no studies about A(H1)pdm09 epidemiology in the Philippines, where year-round influenza activity was observed.

Objectives

We aimed to investigate the epidemiological and clinical features of A(H1)pdm09 in pandemic and post-pandemic periods.

Methods

Data were collected under enhanced surveillance of influenza-like illness (ILI) and severe acute respiratory infection (SARI) from January 2009 to December 2010. RT-PCR was used to detect A(H1)pdm09, following the protocol of the United States Centers for Disease Control and Prevention. The reproduction number was computed as a simple exponential growth rate. Differences in proportional and categorical data were examined using chi-square test or Fishers’ exact test.

Results and Conclusions

The outbreak was observed from week 25 to 35 in 2009 and from week 24 to 37 in 2010. The highest proportion of cases was among children aged 5–14 years. The number of ILI outpatients was 2.3-fold higher in 2009 than in 2010, while the number of inpatients was 1.8-fold higher in 2009. No significant difference in gender was observed during the two periods. The clinical condition of all patients was generally mild and self-limiting, with only 2 mortalities among inpatients in 2009. The basic reproduction number was estimated as 1.16 in 2009 and 1.05 in 2010 in the assumption of mean generation time as 2.6 days. School children played a significant role in facilitating influenza transmission.

Detection of enterovirus 68 in serum from pediatric patients with pneumonia and their clinical outcomes

Enterovirus 68 (EV68) infection occasionally manifests with fatal outcomes. However, detection of EV68 in serum and its clinical outcomes are yet to be determined. In this study, we retrospectively tested stored serum samples collected from pediatric pneumonia patients whose nasopharyngeal specimens were positive for EV68. Of total 28 nasopharyngeal sample-positive patients, EV68 was detected in serum samples among 12 (43%) patients aged between 1 and 4 years. Our results suggest that EV68 can cause viremia by which the virus may exhibit systemic manifestations.

[Infectious disease surveillance in Miyagi after the Great East Japan Earthquake]

OBJECTIVES

The Great East Japan Earthquake, which occurred on March 11, 2011, damaged many health facilities and compelled many inhabitants to live in evacuation centers. For the purpose of monitoring infectious disease outbreaks, infectious disease surveillance targeted at evacuation centers was established in Miyagi Prefecture. In this study, we summarized the monitoring activities of infectious diseases through this surveillance after the earthquake.

METHODS

Infectious disease surveillance was implemented from March 18 to November 6, 2011. The surveillance consisted of two phases (hereafter, surveillance 1 and 2) reflecting the difference in frequencies of reporting as well as the number of targeted diseases. Surveillance 1 operated between March 18 and May 13, 2011, and Surveillance 2 operated between May 10 and November 6, 2011. We reviewed the number of cases reported, the number of evacuation centers, and demographic information of evacuees with the surveillance.

RESULTS

In Surveillance 1, there were 8,737 reported cases; 84% of them were acute respiratory symptoms, and 16% were acute digestive symptoms. Only 4.4% of evacuation centers were covered by the surveillance one week after the earthquake. In Surveillance 2, 1,339 cases were reported; 82% of them were acute respiratory symptoms, and 13% were acute digestive symptoms. Surveillance 2 revealed that the proportion of children aged 5 years and younger was lower than that of other age groups in all targeted diseases. No particular outbreaks were detected through those surveillances.

CONCLUSION

Infectious disease surveillance operated from one week after the earthquake to the closure of all evacuation centers in Miyagi Prefecture. No outbreaks were detected in that period. However, low coverage of evacuation centers just after the earthquake as well as skewed frequencies of reported syndromes draw attention to the improvement of the early warning system. It is important to coordinate with the medical aid team that visits the evacuation centers on a regular basis and to obtain information about the characteristics of evacuees. It is necessary to establish a surveillance system that can monitor infectious disease efficiently from an early phase.

Molecular evolution of the hemagglutinin and neuraminidase genes of pandemic (H1N1) 2009 influenza viruses in Sendai, Japan, during 2009-2011

Analyzing the evolutionary pattern of the influenza A(H1N1)pdm09 strain in different regions is important for understanding its diversification. We therefore conducted this study to elucidate the genetic variability and molecular evolution of the influenza A(H1N1)pdm09 strains that circulated during the 2009-2010 and 2010-2011 influenza seasons in Sendai, Japan. Nasopharyngeal swab specimens were collected from patients with influenza-like illnesses who visited outpatient clinics in Sendai City, Japan, from September 2009 to April 2011. A total of 75 isolates were selected from September 2009 to April 2011 to analyze the genetic changes in the entire hemagglutinin 1 (HA1) segment of the HA gene and the neuraminidase (NA) gene based on sequence analysis. Bayesian coalescent Markov chain Monte Carlo analyses of HA1 and NA gene sequences were performed for further analysis. High sequence identities were observed for HA1 and NA in influenza A(H1N1)pdm09, displaying 99.06 and 99.33 % nucleotide identities, respectively, with the A(H1N1)pdm09 vaccine strain A/California/07/2009. The substitution rates of nucleotides for HA1 in the 2009-2010 and 2010-2011 were 1.5 × 10-3 and 1.6 × 10-3 substitutions per site per year, respectively. Phylogenetic tree analysis demonstrated that Sendai isolates were clustered into global clade 7, which is characterized by an S203T mutation in the HA1 gene. Moreover, two distinct circulation clusters were present in the 2010-2011 season. Mutations were present in antigenic or receptor-binding domains of the HA1 segment, including A141V, S143G, S183P, S185T, and S203T. The Bayesian skyline plot model illustrated a steady rate for the maintenance of genetic diversity, followed by a slight increase in the later part of the 2010-2011 season. Selection analysis revealed that the HA1 (position 197) and NA (position 46) sites were under positive selection; however, no known mutation conferring resistance to NA inhibitors such as H275Y was observed. The effect on control of the influenza A(H1N1)pdm09 virus, including vaccine strain selection, requires continuous monitoring of the strain by genetic surveillance.

Monitoring of influenza viruses in the aftermath of the Great East Japan earthquake

Influenza has a significant impact on public health when a natural disaster occurs during the influenza season. However, the epidemiological characteristics of influenza following natural disasters have not been well documented due to the difficulty of implementing laboratory-based influenza surveillance in such situations. The Great East Japan Earthquake occurred on March 11, 2011, when influenza was already circulating. Since routine influenza surveillance was not performed in Miyagi Prefecture, we initiated an ad hoc laboratory-based monitoring system immediately after the earthquake. From March 15 to May 19, we tested 277 samples for influenza virus collected around Sendai City and from evacuation centers in Miyagi Prefecture. Influenza A (H3N2) was detected in 112 cases, influenza A (H1N1) 2009 in one case, and influenza B in 92 cases. The H3N2 virus was dominant until the 14th week. However, a sudden increase in the number of influenza B cases occurred after schools were reopened. According to phylogenetic analysis, a major clade switch of the H3N2 virus took place after the earthquake. The Yamagata lineage of influenza B was detected in one patient from western Japan, indicating the importing of viruses into the affected area.

Genetic diversity and geographic distribution of genetically distinct rabies viruses in the Philippines

Background

Rabies continues to be a major public health problem in the Philippines, where 200–300 human cases were reported annually between 2001 and 2011. Understanding the phylogeography of rabies viruses is important for establishing a more effective and feasible control strategy.

Methods

We performed a molecular analysis of rabies viruses in the Philippines using rabied animal brain samples. The samples were collected from 11 of 17 regions, which covered three island groups (Luzon, Visayas, and Mindanao). Partial nucleoprotein (N) gene sequencing was performed on 57 samples and complete glycoprotein (G) gene sequencing was performed on 235 samples collected between 2004 and 2010.

Results

The Philippine strains of rabies viruses were included in a distinct phylogenetic cluster, previously named Asian 2b, which appeared to have diverged from the Chinese strain named Asian 2a. The Philippine strains were further divided into three major clades, which were found exclusively in different island groups: clades L, V, and M in Luzon, Visayas, and Mindanao, respectively. Clade L was subdivided into nine subclades (L1–L9) and clade V was subdivided into two subclades (V1 and V2). With a few exceptions, most strains in each subclade were distributed in specific geographic areas. There were also four strains that were divided into two genogroups but were not classified into any of the three major clades, and all four strains were found in the island group of Luzon.

Conclusion

We detected three major clades and two distinct genogroups of rabies viruses in the Philippines. Our data suggest that viruses of each clade and subclade evolved independently in each area without frequent introduction into other areas. An important implication of these data is that geographically targeted dog vaccination using the island group approach may effectively control rabies in the Philippines.

Rabies continues to be a major public health problem in the Philippines. We conducted a molecular epidemiological study of rabies using the complete glycoprotein (G) gene from 235 animal brain samples collected in the Philippines between 2004 and 2010. We identified three major clades and two distinct genogroups in the Philippines. The three major clades L, V, and M were found specifically in the Luzon, Visayas, and Mindanao island groups, respectively. Additionally, two minor genogroups were located in the Luzon island group. These data suggest that although human mediated transmission may have occurred, these virus clades evolved independently after a single introduction into each island group. All of the analyzed Philippine strains were clustered into Asian 2b, which diverged from the Chinese strain Asian 2a. No recent introduction of rabies into the Philippines from other countries was apparent. The elimination of rabies by 2020 is a national goal in the Philippines, necessitating urgent development of a more effective and feasible strategy for controlling rabies. Our findings indicate that a geographically targeted dog vaccination campaign may effectively control rabies in island nations such as the Philippines.

Impact of the Tohoku earthquake and tsunami on pneumonia hospitalisations and mortality among adults in northern Miyagi, Japan: a multicentre observational study

Background

On 11 March 2011, the Tohoku earthquake and tsunami struck off the coast of northeastern Japan. Within 3 weeks, an increased number of pneumonia admissions and deaths occurred in local hospitals.

Methods

A multicentre survey was conducted at three hospitals in Kesennuma City (population 74 000), northern Miyagi Prefecture. All adults aged ≥18 years hospitalised between March 2010 and June 2011 with community-acquired pneumonia were identified using hospital databases and medical records. Segmented regression analyses were used to quantify changes in the incidence of pneumonia.

Results

A total of 550 pneumonia hospitalisations were identified, including 325 during the pre-disaster period and 225 cases during the post-disaster period. The majority (90%) of the post-disaster pneumonia patients were aged ≥65 years, and only eight cases (3.6%) were associated with near-drowning in the tsunami waters. The clinical pattern and causative pathogens were almost identical among the pre-disaster and post-disaster pneumonia patients. A marked increase in the incidence of pneumonia was observed during the 3-month period following the disaster; the weekly incidence rates of pneumonia hospitalisations and pneumonia-associated deaths increased by 5.7 times (95% CI 3.9 to 8.4) and 8.9 times (95% CI 4.4 to 17.8), respectively. The increases were largest among residents in nursing homes followed by those in evacuation shelters.

Conclusions

A substantial increase in the pneumonia burden was observed among adults after the Tohoku earthquake and tsunami. Although the exact cause remains unresolved, multiple factors including population aging and stressful living conditions likely contributed to this pneumonia outbreak.

Knowledge, attitudes, and practices survey of rabies in a community in Sri Lanka

OBJECTIVES

The primary objective of this study was to determine the level of knowledge, attitudes and practices (KAP) of rabies management and control of a sample population. The secondary objective was to compare the KAP with respect to rabies management and control between urban and rural areas and between pet and non-pet owners.

METHODS

This cross-sectional study was carried out by conducting face-to-face interviews using structured questionnaires among 1570 respondents from selected households in the Kandy District, Sri Landa.

RESULTS

Approximately 58% of the sample population was pet owners. Among all the respondents, there was a high level of awareness (90%) that dogs are the most common rabies reservoir, that the disease is fatal (79%), and that rabies can be prevented by vaccination (88%). Most of the subjects (96%) would seek treatment from a doctor or a hospital after being bitten by a dog. Although 76% of the respondents said that their pet dogs were vaccinated, only one-half were able to present a vaccination certificate upon request. The subjects from the urban areas would submit the head of an animal for rabies evaluation (69%) compared with those from the rural areas (57%). Pet owners (93%) are more aware that dog rabies vaccines are available from authorized offices than non-pet owners (87%).

CONCLUSIONS

The level of awareness of rabies and the level of receptiveness to rabies control measures are high. There is a difference in the attitudes and pet care practices relevant to rabies control between urban and rural areas. Pet owners tend to be more cooperative to rabies control activities. The attitudes and practices of the respondents may reflect the inaccessibility of facilities and the lack of services that would enable community participation in rabies control.

Infectious diseases following natural disasters: prevention and control measures

Natural disasters may lead to infectious disease outbreaks when they result in substantial population displacement and exacerbate synergic risk factors (change in the environment, in human conditions and in the vulnerability to existing pathogens) for disease transmission. We reviewed risk factors and potential infectious diseases resulting from prolonged secondary effects of major natural disasters that occurred from 2000 to 2011. Natural disasters including floods, tsunamis, earthquakes, tropical cyclones (e.g., hurricanes and typhoons) and tornadoes have been secondarily described with the following infectious diseases including diarrheal diseases, acute respiratory infections, malaria, leptospirosis, measles, dengue fever, viral hepatitis, typhoid fever, meningitis, as well as tetanus and cutaneous mucormycosis. Risk assessment is essential in post-disaster situations and the rapid implementation of control measures through re-establishment and improvement of primary healthcare delivery should be given high priority, especially in the absence of pre-disaster surveillance data.

Influenza transmission in a community during a seasonal influenza A(H3N2) outbreak (2010-2011) in Mongolia: a community-based prospective cohort study

Background

Knowledge of how influenza viruses spread in a community is important for planning and implementation of effective interventions, including social distancing measures. Households and schools are implicated as the major sites for influenza virus transmission. However, the overall picture of community transmission is not well defined during actual outbreaks. We conducted a community-based prospective cohort study to describe the transmission characteristics of influenza in Mongolia.

Methods and Findings

A total of 5,655 residents in 1,343 households were included in this cohort study. An active search for cases of influenza-like illness (ILI) was performed between October 2010 and April 2011. Data collected during a community outbreak of influenza A(H3N2) were analyzed. Total 282 ILI cases occurred during this period, and 73% of the subjects were aged <15 years. The highest attack rate (20.4%) was in those aged 1–4 years, whereas the attack rate in those aged 5–9 years was 10.8%. Fifty-one secondary cases occurred among 900 household contacts from 43 households (43 index cases), giving an overall crude household secondary attack rate (SAR) of 5.7%. SAR was significantly higher in younger household contacts (relative risk for those aged <1 year: 9.90, 1–4 years: 5.59, and 5–9 years: 6.43). We analyzed the transmission patterns among households and a community and repeated transmissions were detected between households, preschools, and schools. Children aged 1–4 years played an important role in influenza transmission in households and in the community at large. Working-age adults were also a source of influenza in households, whereas elderly cases (aged ≥65 years) had no link with household transmission.

Conclusions

Repeated transmissions between households, preschools, and schools were observed during an influenza A(H3N2) outbreak period in Mongolia, where subjects aged 1–4 years played an important role in influenza transmission.

Detection of human rhinovirus C viral genome in blood among children with severe respiratory infections in the Philippines

Human rhinovirus (HRV) C was recently identified as the third species of HRV using a molecular technique. Infections caused by previously identified HRVs (A and B) are thought to be limited to the respiratory tract; however, pathogenesis of HRVC is still largely unknown. A total of 816 nasopharyngeal swabs from hospitalized children with severe respiratory infections in the Philippines (May 2008-May 2009) were tested for HRV by reverse transcription polymerase chain reaction (RT-PCR), and 243 samples (29.8%) were positive for HRV. Among these patients, serum samples were also tested to determine whether specific HRV species were associated with viremia. Only 30 serum samples (12.3%) were positive for HRV. However, the HRV positive rates were different among HRV species, 3% (4/135) for HRVA, 0% (0/25) for HRVB, and 31% (26/83) for HRVC, and were the highest on 2 days after the onset of symptoms. These results suggest that HRVC may have a different pathogenicity and can more commonly cause viremia than HRVA and HRVB. Serum positive rates for HRV are affected by age, i.e., higher positive rates for those aged 1 year or more. HRVC that were detected from serum exhibited the same level of sequence diversity as those positive only for nasopharyngeal samples in phylogenetic analysis. However, all HRVA which were detected from serum were clustered in a monophyletic clade based on their 5' non-coding region (NCR) sequences, which is closely related with a certain HRVC genotype (A2) in 5'-NCR. This finding suggests that the 5'NCR region may be associated with viremia.

Viruses that cross borders: factors responsible for global dissemination of viral infections

Objective

Pandemic viral infections as emerging infectious diseases are of a great global concern. However, for some viruses, particular strains are endemic to specific areas and can be genetically distinguished from strains in other regions. In contrast, for some other viruses, genetically similar strains can spread and circulate all over the world. This study addresses global dissemination of various viral infections.

Methods

We classified 34 viruses as per their ability to cross borders by review. We also described factors responsible for and the dynamics of global dissemination. We examined biological characteristics of viruses, manners or routes of transmission, host responses and epidemiological factors.

Results

Factors required for viruses to cross borders include ‘non-blood infection’, ‘short incubation period’, ‘short infectious period’, ’frequent re-infection’, ‘small basic reproductive number (R₀)’ and ‘high annual incidence’.

Conclusion

Knowing the factors responsible for global dissemination of pathogens is useful for controlling and/or containing both classic and emerging infectious diseases.

[Lessons learned from pandemic (H1N1) 2009: Japan and global prospective]

Currently there have reported pandemic (H1N1) 2009 over 200 countries and areas globally with more than 16,813 victims according to World Health Organization. Demographic characterization of those cases seemed to be consistent around the world that is higher incidence among school age children and higher mortality rate among elderly. Uniquely Japan has lower mortality rate compared with other countries. Based upon pandemic preparedness plan, several interventions such as personal hygiene and social distancing as well as clinical management were implemented since the beginning of pandemic. Of particular, school closure was continuously implemented during pandemic and medical access for influenza like illness cases was sustained with administration of antivirals in Japan. It is important to identify some gaps in the implementation of interventions for further preparedness.