Original Article: Decline of notified dengue infections in Indonesia in 2017: Discussion of the possible determinants

Effects of El Niño and the Positive Indian Ocean Dipole (+IOD) on Health, Food Security, Economics, and Conflict in Low- and Middle-Income Countries in the Indo-Pacific: A Systematic Review

Climate drivers such as the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) can impact multiple sectors globally. We are currently witnessing the effects of these teleconnections against the backdrop of a changing climate. This systematic review takes stock of the available evidence on compounding and cascading effects of El Niño and the Positive IOD on health, economic, migration, conflicts, and nutrition outcomes in low- and middle-income countries from the Indo-Pacific region. The review sheds light on how effects vary between and within the considered countries and explores potential sources of heterogeneity. The search of studies was carried out in January 2024 in 12 major databases/search engines and 14 institutional websites, using English keywords, and paired by forward and backward citation tracking of the included studies. The review's inclusion criteria encompassed quantitative studies as long as they provide an estimate of relationship between the climate driver and outcome, and qualitative studies that aim to infer causation such as realist evaluation or process tracing. The analysis used a combination of meta-analysis with random-effects models, median effects from correlational and regression studies, and narrative synthesis. We found that El Niño is likely to decrease agricultural production and productivity at the Indo-Pacific level, although the analysed studies are highly diverse. The absence of evidence on the effects of the considered climate drivers on migration, conflict, food security and nutrition is an important evidence gap. We found limited evidence on the differential effects by El Niño's and +IOD's magnitude and no studies examining their combined impact or qualitative effectiveness studies. The high risk of bias detected across studies calls for more thorough attention to study design, conduct, and reporting in answering questions about effects. Despite remaining evidence gaps, this review highlights potential effects of El Niño and +IOD in the Indo-Pacific and underscores the need for context-specific policy responses to mitigate risks at local and regional levels. Caution is warranted in interpreting the overall findings given the generally high risk of bias of evidence.

Spatial patterns and clustering of dengue incidence in Mexico: Analysis of Moran's index across 2,471 municipalities from 2022 to 2024

Dengue is an increasing public health challenge, with rising cases and expanding distribution. Its complex epidemiology is influenced by climate change, urbanization, and the circulation of multiple viral serotypes. This study aimed to characterize the spatial and temporal (2022-2024) patterns of dengue incidence across 2,471 municipalities in Mexico. Weekly case counts, obtained through the normative epidemiological surveillance system for vector-borne diseases, were used to calculate incidence rates per 100,000 population. Geographic Information Systems were employed to analyze spatial patterns, while Local Moran's I statistic and a k-nearest neighbors spatial weights matrix identified spatial clusters. A total of 622,689 dengue cases were analyzed, with incidence rates rising from 29.4 in 2022 to 279.0 per 100,000 in 2024. Dengue transmission expanded, affecting 38.0% of municipalities in 2022 and 68.6% by 2024 ([Formula: see text] < 0.001). Spatial clustering also increased, with positive clusters increasing from 28 municipalities in 2022-98 in both 2023 and 2024. Moran's I values indicated a peak in spatial autocorrelation in 2023 (I = 0.57). While DENV-2 was the predominant serotype in 2022, DENV-3 became dominant in 2023 and 2024. Over time, high-incidence areas shifted from southern and central regions to the southeast and Pacific coast. These findings suggest the growing burden of dengue in Mexico, driven by rising incidence, expanding geographic distribution, and evolving spatial patterns. A coordinated public health response is needed to mitigate the impact of dengue and prevent its spread to newly affected areas.

Dengue dynamics in Bali: Serotype shifts, genotype replacement and multiple virus lineage circulation in the last 10 years

BACKGROUND

Bali, one of the world's most popular tourist destinations, is hyper-endemic to dengue, an acute febrile illness caused by infection with dengue virus (DENV). Outbreaks of dengue occur annually with worrisome rates of morbidity and mortality. Despite this, comprehensive and continuous virus surveillance is yet to be established. We conducted DENV serotype and genotype surveillance in Bali to monitor viral transmission dynamics.

METHODS

We enrolled febrile patients with dengue clinical symptoms in hospitals in Denpasar, Bali. Clinical evaluations and laboratory assessments were conducted, and blood samples were collected. DENV serotypes were determined using RT-PCR, and genotyping was performed by sequencing the envelope protein gene and the complete genomes. Subsequently, phylogenetic analyses were conducted to analyse the recent data alongside retrospective sequence data.

RESULTS

A total of 62 and 66 dengue patients were recruited during 2018-2020 and 2022, and from these, we obtained DENV serotype data for 49 and 48 individuals, respectively. Among the DENV analysed, the most prevalent serotype in 2018-2020 was DENV-1 (30%) and shifted to DENV-3 (57.6%) in 2022. When compared to data from the last 10 years, serotype shifting was clearly observed. We sequenced the genomes of 60 isolates and observed the presence of multiple virus lineages and the replacement of Genotype IV of DENV-1 with Genotype I. The Cosmopolitan, Genotype I and Genotype II remained the predominant genotypes for DENV-2, DENV-3 and DENV-4, respectively.

CONCLUSION

We reveal that DENV serotype predominance in Bali has been shifting in the past 10 years. While genotype replacement occurred, continuous circulation of local endemic viruses was responsible for the annual outbreak of dengue. These findings indicate the genetic diversity and dynamic nature of DENV circulating in Bali. Routine virus surveillance is important to understand the cyclical patterns of DENV serotypes that is useful to predict the future outbreaks.

Risk of Uveitis in Dengue Fever Patients: A Population-Based Cohort Study in Taiwan

Dengue-related ocular complications were considered rare, but recent evidence points to a broader spectrum of manifestations, including uveitis. This study utilized the Taiwan National Health Insurance Research Database (NHIRD) to investigate the incidence of uveitis in dengue patients, aiming to fill this research gap. This population-based, retrospective cohort study utilized the Taiwan National Health Insurance Research Database (NHIRD) and included patients with and without Dengue fever. The non-Dengue fever cohort comprised randomly selected control patients who were matched. Hazard ratios and Kaplan-Meier analysis were conducted to compare the incidence of uveitis in the Dengue and non-Dengue cohorts. Subgroup analyses were carried out based on age groups, genders, and comorbidities. A total of 26 950 patients diagnosed with Dengue fever were included in the study (49.6% female, mean age at index 41.63 years). Based on a 1:4 matching ratio, 107 800 control subjects without uveitis (50.03% female, mean age at index 41.41 years) were also included. The adjusted hazard ratio (aHR) of uveitis was higher in the Dengue fever group than in the non-Dengue fever group (aHR = 1.38, p < 0.001). A history of stroke or transient ischemic attack (TIA) was not associated with uveitis. Stratified analyses revealed that patients with Dengue fever had an increased risk regardless of their sex and age. The Kaplan-Meier method with the log-rank test showed a significantly higher cumulative incidence of uveitis in the Dengue fever cohort than in the non-Dengue fever cohort (p < 0.001). In the subgroup analysis for most major comorbidities, the significantly higher risk for uveitis in those patients with Dengue fever, was only demonstrated in the subgroups of those without these major comorbidities. Our findings showed Dengue infection to be associated with increased risk for uveitis. Clinicians should be attentive to a history of stroke or TIA in patients with Dengue fever.

Dengue virus and the 2024 Paris Olympics

The 2024 Paris Olympics and Paralympics face concerns over dengue virus transmission, despite Paris's lower mosquito activity. Preventive measures include eliminating breeding sites, insecticide spraying, and public awareness. Health systems will monitor and respond to cases. Large gatherings like the Olympics can amplify disease spread, as seen with Zika in Rio 2016. Recent reports confirm dengue presence in Europe, highlighting global risks. While Paris's overall dengue risk is low, even a few cases could impact global health. Collaboration among health authorities, researchers, and event organizers is crucial to ensure participant and public safety during the games.

Evaluation of in-house dengue real-time PCR assays in West Java, Indonesia

Dengue is an infectious disease caused by infection of dengue virus (DENV) transmitted by Aedes aegypti and Aedes albopictus. In Indonesia, dengue commonly occurs with an increasing incidence rate annually. It is known that early detection of dengue infection is one of the keys to controlling this disease outbreak. Rapid and accurate early detection to diagnose dengue can be achieved by molecular tests, one of which is through a real-time PCR method. However, real-time PCR assay for dengue developed based on Indonesian DENV sequences has not been available. Therefore, we developed in-house dengue real-time PCR (SYBR- and TaqMan-based) assays and evaluated those assays in routine clinical testing in the community. These assays target the 3' UTR region of the four DENV serotypes and was found to be specific for DENV. The most sensitive assay was the TaqMan assay with the LOD95% of 482 copy/ml, followed by the SYBR assay with the LOD95% of 14,398 copy/ml. We recruited dengue suspected patients from three primary health care services in West Java, Indonesia to represent the community testing setting. Dengue infection was examined using the two in-house real-time PCR assays along with NS1, IgM, and IgG rapid diagnostic tests (RDT). In total, as many as 74 clinical specimens of dengue suspected patients were included in this study. Among those patients, 21 were positive for TaqMan assay, 17 were positive for SYBR assay, nine were positive for NS1 test, six were positive for both IgG and IgM tests, and 22 were positive for IgG test only. Compared with our in-house TaqMan assay, the sensitivity of NS1 test, IgM test, and IgG test were 42.86%, 14.29%, and 28.57% respectively. Among these three RDT tests, NS1 showed 100% specificity. Thus, our study confirmed that NS1 test showed high specificity, indicating that a positive result of NS1 can be confidently considered a dengue case. However, NS1, IgM, and IgG tests with RDT are not enough to diagnose a dengue case. We suggest applying the high sensitivity and specificity rRT-PCR test as the gold standard for early detection and antibody test as a follow-up test for rRT-PCR negative cases.

Dengue outbreaks in a city with recent transmission in São Paulo state, Brazil

We investigated the distribution of dengue cases, solid waste deposits (SWDs), forest fragments, water drainage, population income, and the possible association with dengue outbreaks in Presidente Prudente, São Paulo, Brazil. An urban setting with recent transmission. Data were obtained from public agencies. Kernel density maps of the variables were constructed. From 2015 to 2021, 33026 cases of dengue were reported; the incidence and mortality rate were highest in 2016. The number of cases decreased during the COVID-19 pandemic (2020 and 2021) compared with 2019, but alarming rates were registered in 2022. In 2015, 56 points of SWDs were identified, with an increase of 1.6-fold in 2020 and 2021. Multivariate analysis showed a positive correlation between the density of dengue cases and SWDs with the highest correlation (0.70) in 2020. Identifying these areas could guide public health authorities in surveillance measures and improvements in health care infrastructure.

Dengue fever ophthalmic manifestations: A review and update

Dengue fever, the most common arbovirus disease, affects an estimated 390 million people annually. Dengue virus (DENV) is an RNA virus of the Flaviviridae family with four different serotypes. Dengue haemorrhagic fever is the deadliest form of dengue infection and is characterised by thrombocytopaenia, hypotension, and the possibility of multi-system organ failure. The mechanism hypothesised for DENV viral replication is intrinsic antibody-dependent enhancement, which refers to Fcγ receptor-mediated viral amplification. This hypothesis suggests that the internalisation of DENV through the Fcγ receptor inhibits antiviral genes by suppressing type-1 interferon-mediated antiviral responses. DENV NS1 antibodies can promote the release of various inflammatory mediators in the nuclear transcription factor pathway (NF-κB-dependent), including monocyte chemoattractant protein (MCP)-1, interleukin (IL)-6, and IL-8. As a result, MCP-1 increases ICAM-1 expression and facilitates leukocyte transmigration. In addition, anti-DENV NS1 antibodies induce endothelial cell apoptosis via a nitric oxide-regulated pathway. A chain reaction involving pre-existing DENV heterotypic antibodies and innate immune cells causes dysfunction in complement system activity and contributes to the action of autoantibodies and anti-endothelial cells, resulting in endothelial cell dysfunction, blood-retinal barrier breakdown, haemorrhage, and plasma leakage. A spectrum of ocular diseases associated with DENV infection, ranging from haemorrhagic to inflammatory manifestations, has been reported in the literature. Although rare, ophthalmic manifestations can occur in both the anterior and posterior segments and are usually associated with thrombocytopenia. The most common ocular complication is haemorrhage. However, ophthalmic complications, such as anterior uveitis and vasculitis, suggest an immune-mediated pathogenesis.

Spatial differentiation and determinants of COVID-19 in Indonesia

BACKGROUND

The spread of the coronavirus disease 2019 (COVID-19) has increasingly agonized daily lives worldwide. As an archipelagic country, Indonesia has various physical and social environments, which implies that each region has a different response to the pandemic. This study aims to analyze the spatial differentiation of COVID-19 in Indonesia and its interactions with socioenvironmental factors.

METHODS

The socioenvironmental factors include seven variables, namely, the internet development index, literacy index, average temperature, urban index, poverty rate, population density (PD) and commuter worker (CW) rate. The multiple linear regression (MLR) and geographically weighted regression (GWR) models are used to analyze the impact of the socioenvironmental factors on COVID-19 cases. COVID-19 data is obtained from the Indonesian Ministry of Health until November 30th 2020.

RESULTS

Results show that the COVID-19 cases in Indonesia are concentrated in Java, which is a densely populated area with high urbanization and industrialization. The other provinces with numerous confirmed COVID-19 cases include South Sulawesi, Bali, and North Sumatra. This study shows that the socioenvironmental factors, simultaneously, influence the increasing of confirmed COVID-19 cases in the 34 provinces of Indonesia. Spatial interactions between the variables in the GWR model are relatively better than those between the variables in the MLR model. The highest spatial tendency is observed outside Java, such as in East Nusa Tenggara, West Nusa Tenggara, and Bali.

CONCLUSION

Priority for mitigation and outbreak management should be high in areas with high PD, urbanized spaces, and CW.

Epidemiology of Indigenous Dengue Cases in Zhejiang Province, Southeast China

Objective

Autochthonous transmission of the dengue virus (DENV) occurred each year from 2014 to 2018 in Zhejiang province, and became an emerging public health problem. We characterized the autochthonous transmission of the DENV and traced the source of infection for further control and prevention of dengue.

Methods

Descriptive and spatiotemporal cluster analyses were conducted to characterize the epidemiology of autochthonous transmission of the DENV. Molecular epidemiology was used to identify the infection source.

Results

In total, 1,654 indigenous cases and 12 outbreaks, with no deaths, were reported during 2004-2018. Before 2017, all outbreaks occurred in suburban areas. During 2017-2018, five out of eight outbreaks occurred in urban areas. The median duration of outbreaks (28 days) in 2017-2018 was shortened significantly (P = 0.028) in comparison with that in 2004-2016 (71 days). The median onset-visiting time, visiting-confirmation time, and onset-confirmation time was 1, 3, and 4 days, respectively. The DENV serotypes responsible for autochthonous transmission in Zhejiang Province were DENV 1, DENV 2, and DENV 3, with DENV 1 being the most frequently reported. Southeast Asia was the predominant source of indigenous infection.

Conclusions

Zhejiang Province witnessed an increase in the frequency, incidence, and geographic expansion of indigenous Dengue cases in recent years. The more developed coastal and central region of Zhejiang Province was impacted the most.

Hyperendemic Dengue and Possible Zika Circulation in the Westernmost Region of the Indonesian Archipelago

The transmission of dengue and other medically important mosquito-borne viruses in the westernmost region of Indonesia is not well described. We assessed dengue and Zika virus seroprevalence in Aceh province, the westernmost area of the Indonesian archipelago. Serum samples collected from 199 randomly sampled healthy residents of Aceh Jaya in 2017 were analyzed for neutralizing antibodies by plaque reduction neutralization test (PRNT). Almost all study participants (198/199; 99.5%) presented with multitypic profiles of neutralizing antibodies to two or more DENV serotypes, indicating transmission of multiple DENV in the region prior to 2017. All residents were exposed to one or more DENV serotypes by the age of 30 years. The highest geometric mean titers were measured for DENV-4, followed by DENV-1, DENV-2 and DENV-3. Among a subset of 116 sera, 27 neutralized ZIKV with a high stringency (20 with PRNT90 > 10 and 7 with PRNT90 > 40). This study showed that DENV is hyperendemic in the westernmost region of the Indonesian archipelago and suggested that ZIKV may have circulated prior to 2017.

Co-Circulation of Chikungunya and Multiple DENV Serotypes and Genotypes, Western Indonesia 2015-2016

Dengue is a mosquito-borne disease of public health concern affecting tropical and subtropical countries, including Indonesia. Although studies on dengue epidemiology have been undertaken in Indonesia, data are lacking in many areas of the country. The aim of this study was to determine dengue virus (DENV) and chikungunya virus (CHIKV) molecular epidemiology in western regions of the Indonesian archipelago. A one-year prospective study was conducted in Aceh and Jambi in 2015 and 2016, respectively, where patients with dengue-like illness were enrolled. Of 205 patients recruited, 29 and 27 were confirmed with dengue in Aceh and Jambi, respectively, and three from Jambi were confirmed with chikungunya. DENV-1 was the predominant serotype identified in Aceh while DENV-2 was predominant in Jambi. All DENV-1 and DENV-2 from both regions were classified as Genotype I and Cosmopolitan genotype, respectively, and all DENV-3 viruses from Jambi were Genotype I. Some viruses, in particular DENV-1, displayed a distinct lineage distribution, where two DENV-1 lineages from Aceh were more closely related to viruses from China instead of Jambi highlighting the role of travel and flight patterns on DENV transmission in the region. DENV-2 from both Aceh and Jambi and DENV-3 from Jambi were all closely related to Indonesian local strains. All three CHIKV belonged to Asian genotype and clustered closely with Indonesian CHIKV strains including those previously circulating in Jambi in 2015, confirming continuous and sustainable transmission of CHIKV in the region. The study results emphasize the importance of continuous epidemiological surveillance of arboviruses in Indonesia and simultaneous testing for CHIKV among dengue-suspected patients.

Are Temperature Suitability and Socioeconomic Factors Reliable Predictors of Dengue Transmission in Brazil?

Dengue is an ongoing problem, especially in tropical countries. Like many other vector-borne diseases, the spread of dengue is driven by a myriad of climate and socioeconomic factors. Within developing countries, heterogeneities on socioeconomic factors are expected to create variable conditions for dengue transmission. However, the relative role of socioeconomic characteristics and their association with climate in determining dengue prevalence are poorly understood. Here we assembled essential socioeconomic factors over 5570 municipalities across Brazil and assessed their effect on dengue prevalence jointly with a previously predicted temperature suitability for transmission. Using a simultaneous autoregressive approach (SAR), we showed that the variability in the prevalence of dengue cases across Brazil is primarily explained by the combined effect of climate and socioeconomic factors. At some dengue seasons, the effect of temperature on transmission potential showed to be a more significant proxy of dengue cases. Still, socioeconomic factors explained the later increase in dengue prevalence over Brazil. In a heterogeneous country such as Brazil, recognizing the transmission drivers by vectors is a fundamental issue in effectively predicting and combating tropical diseases like dengue. Ultimately, it indicates that not considering socioeconomic factors in disease transmission predictions might compromise efficient surveillance strategies. Our study shows that sanitation, urbanization, and GDP are regional indicators that should be considered along with temperature suitability on dengue transmission, setting effective directions to mosquito-borne disease control.