The impact of COVID-19 lockdown on dengue transmission in Sri Lanka; A natural experiment for understanding the influence of human mobility

Unraveling varying spatiotemporal patterns of dengue and associated exposure-response relationships with environmental variables in Southeast Asian countries before and during COVID-19

The enforcement of COVID-19 interventions by diverse governmental bodies, coupled with the indirect impact of COVID-19 on short-term environmental changes (e.g. plant shutdowns lead to lower greenhouse gas emissions), influences the dengue vector. This provides a unique opportunity to investigate the impact of COVID-19 on dengue transmission and generate insights to guide more targeted prevention measures. We aim to compare dengue transmission patterns and the exposure-response relationship of environmental variables and dengue incidence in the pre- and during-COVID-19 to identify variations and assess the impact of COVID-19 on dengue transmission. We initially visualized the overall trend of dengue transmission from 2012-2022, then conducted two quantitative analyses to compare dengue transmission pre-COVID-19 (2017-2019) and during-COVID-19 (2020-2022). These analyses included time series analysis to assess dengue seasonality, and a Distributed Lag Non-linear Model (DLNM) to quantify the exposure-response relationship between environmental variables and dengue incidence. We observed that all subregions in Thailand exhibited remarkable synchrony with a similar annual trend except 2021. Cyclic and seasonal patterns of dengue remained consistent pre- and during-COVID-19. Monthly dengue incidence in three countries varied significantly. Singapore witnessed a notable surge during-COVID-19, particularly from May to August, with cases multiplying several times compared to pre-COVID-19, while seasonality of Malaysia weakened. Exposure-response relationships of dengue and environmental variables show varying degrees of change, notably in Northern Thailand, where the peak relative risk for the maximum temperature-dengue relationship rose from about 3 to 17, and the max RR of overall cumulative association 0-3 months of relative humidity increased from around 5 to 55. Our study is the first to compare dengue transmission patterns and their relationship with environmental variables before and during COVID-19, showing that COVID-19 has affected dengue transmission at both the national and regional level, and has altered the exposure-response relationship between dengue and the environment.

Sri Lanka's COVID-19 response and maintaining health services: implications for future pandemics

This study examines how Sri Lanka, a lower-middle income country, managed its COVID-19 response and maintained health services. It draws on an extensive document review, key informant interviews and a national survey of public experience and opinion to assess what Sri Lanka did, its effectiveness and why.Owing to a strong health system and luck, Sri Lanka stopped the first wave of COVID-19 infections, and it adopted a 'Zero-COVID' approach with the explicit goal of stopping outbreaks. This was initially effective. Outbreaks reduced healthcare use, but with minimal impact on health outcomes. But from end-2020, Sri Lanka switched its approach to tolerating transmission and mitigation. It took proactive actions to maintain healthcare access, and it pursued a COVID-19 vaccination effort that was successful in covering its adult population rapidly and with minimal disparities. Despite this, widespread transmission during 2021-2022 disrupted health services through the pressure on health facilities of patients with COVID-19 and infection of healthcare workers, and because COVID-19 anxiety discouraged patients from seeking healthcare. This led to substantial mortality and more than 30 000 excess deaths by 2022.We find that Sri Lanka abandoned its initially successful approach, because it failed to understand that its chosen strategy required symptomatic PCR testing in primary care. Failure to invest in testing was compounded by groupthink and a medical culture averse to testing.Sri Lanka's experience confirms that strong public health capacities, robust healthcare systems and intersectoral action are critical for pandemic response. It shows that civilian-military collaboration can be beneficial but contested, and that lack of fiscal space will undermine any response. It also demonstrates that pandemic preparedness cannot guarantee a successful pandemic response. Policy and research must pay more attention to improving decision-making processes when faced with pandemics involving novel pathogens, rapid spread, and substantial scientific uncertainty.

Assessing the Burden of Dengue during the COVID-19 Pandemic in Mexico

The transmission of the dengue virus in Mexico has historically been high, and its burden during the COVID-19 pandemic is currently not well understood. Our objective was to assess the burden of dengue-related disability-adjusted life years (DALYs) between 2020 and 2022. We conducted a cross-sectional analysis of databases resulting from an epidemiological surveillance of vector-borne diseases and computed DALYs using the protocol of the Global Burden of Disease (GBD) study 2019. Our results showed that there were 218,807 incident cases of dengue during the study period, resulting in 951 deaths. The calculated DALYs (and their 95% confidence intervals) were 8121 (7897-8396), 4733 (4661-4820), and 8461 (8344-8605) in 2020, 2021, and 2022, respectively. The DALY rates (per 100,000) were 6.5 (6.3-6.6), 3.8 (3.7-3.9), and 6.7 (6.6-6.8), respectively. The rates for 2020 and 2022 were similar to the historical mean (6.4, p = 0.884), whereas the rate for 2021 was lower than the mean. Premature mortality (years of life lost, YLL) contributed to 91% of the total burden. Our findings suggest that dengue fever remained a significant cause of disease burden during the COVID-19 pandemic, especially in terms of premature mortality.

Introductory Chapter: Lessons from SARS-CoV-2/COVID-19 after Two Years of Pandemic

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Cross-reactivity of SARS-CoV-2 with other pathogens, especially dengue virus: A historical perspective

Dengue is a vector-borne viral disease caused by a Flavivirus whereas the COVID-19 pandemic was caused by a highly contagious virus, SARS-CoV-2 belonging to the family Coronaviridae. However, COVID-19 severity was observably less in dengue-endemic countries and vice versa especially during the active years of the pandemic (2019-2021). We observed that dengue virus (DENV) antibodies (Abs) could cross-react with SARS-CoV-2 spike antigen. This resulted in SARS-CoV-2 false positivity by rapid Ab test kits. DENV Abs binding to SARS-CoV-2 receptor-binding domain (and the reverse scenario), as revealed by docking studies further validated DENV and SARS-CoV-2 cross-reactivity. Finally, SARS-CoV-2 Abs were found to cross-neutralize DENV1 and DENV2 in virus neutralization test (VNT). Abs to other pathogens like Plasmodium were also cross-reactive but non-neutralizing for SARS-CoV-2. Here, we analyze the existing data on SARS-CoV-2 cross-reactivity with other pathogens, especially dengue to assess its impact on health (cross-protection?) and differential sero-diagnosis/surveillance.

Effects of different levels of non-pharmaceutical interventions on hand, foot and mouth disease in Guangzhou, China

BACKGROUND

Non-pharmaceutical interventions (NPIs) against coronavirus disease 2019 (COVID-19) may have suppressed the transmission of other infectious diseases. This study aimed to evaluate the impact of different degrees of NPIs during the COVID-19 pandemic on hand, foot and mouth disease (HFMD) in Guangzhou, China.

METHODS

Weekly reported HFMD cases and pathogens information during 2015-2021 in Guangzhou were collected from the China National Notifiable Disease Reporting System. The observed number of HFMD cases in 2020 and 2021 was compared to the average level in the same period during 2015-2019. Then, an interrupted time-series segmented regression analysis was applied to estimate the impact of NPIs on HFMD, such as social distancing, suspension of schools, community management and mask wearing. The effects across different subgroups stratified by gender, children groups and enterovirus subtype of HFMD were also examined.

RESULTS

A total of 13,224 and 36,353 HFMD cases were reported in 2020 and 2021, which decreased by 80.80% and 15.06% respectively compared with the average number of cases in the same period during 2015-2019. A significant drop in the number of HFMD cases during time when strict NPIs were applied (relative change: 69.07% [95% confidence interval (CI): 68.84%-69.30%]). The HFMD incidence rebounded to historical levels in 2021 as the lockdown eased. The slightest reduction of HFMD cases was found among children at kindergartens or childcare centres among the three children groups (children at kindergartens or childcare centres: 55.50% [95% CI: 54.96%-56.03%]; children living at home: 72.64% [95% CI: 72.38%-72.89%]; others: 74.06% [95% CI: 73.19%-74.91%]).

CONCLUSIONS

The strong NPIs during the COVID-19 epidemic may have a significant beneficial effect on mitigating HFMD. However, the incidence of HFMD rebounded as the NPIs became less stringent. Authorities should consider applying these NPIs during HFMD outbreaks and strengthening personal hygiene in routine prevention.

Dengue Incidence and Aedes Vector Collections in Relation to COVID-19 Population Mobility Restrictions

Contrary to expectation, dengue incidence decreased in many countries during the period when stringent population movement restrictions were imposed to combat COVID-19. Using a seasonal autoregressive integrated moving average model, we previously reported a 74% reduction in the predicted number of dengue cases from March 2020 to April 2021 in the whole of Sri Lanka, with reductions occurring in all 25 districts in the country. The reduction in dengue incidence was accompanied by an 87% reduction in larval collections of Aedes vectors in the northern city of Jaffna. It was proposed that movement restrictions led to reduced human contact and blood feeding by Aedes vectors, accompanied by decreased oviposition and vector densities, which were responsible for diminished dengue transmission. These findings are extended in the present study by investigating the relationship between dengue incidence, population movement restrictions, and vector larval collections between May 2021 and July 2022, when movement restrictions began to be lifted, with their complete removal in November 2021. The new findings further support our previous proposal that population movement restrictions imposed during the COVID-19 pandemic reduced dengue transmission primarily by influencing human-Aedes vector interaction dynamics.

COVID-19 serum can be cross-reactive and neutralizing against the dengue virus, as observed by the dengue virus neutralization test

OBJECTIVES

Observing the serological cross-reactivity between SARS-CoV-2 and dengue virus (DV), we aimed to elucidate its effect on dengue serodiagnosis and infectivity in a highly dengue-endemic city in India.

METHODS

A total of 52 COVID-19 (reverse transcription-polymerase chain reaction [RT-PCR] positive) serum samples were tested in rapid lateral flow immunoassays and DV immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) to detect DV or SARS-CoV-2 IgG/immunoglobulin M. The COVID-19 antibody (Ab) positive samples were subjected to a virus neutralization test (Huh7 cells) using DV type 1 (DV1) clinical isolate.

RESULTS

Most (93%) of the SARS-CoV-2 Ab-positive serum samples cross-reacted with DV in rapid or ELISA tests. All were DV RNA and nonstructural protein 1 (NS1) antigen-negative. COVID-19 serum samples that were DV cross-reactive neutralized DV1. Of these, 57% had no evidence of DV pre-exposure (DV NS1 Ab-negative). The computational study also supported potential interactions between SARS-CoV-2 Ab and DV1.

CONCLUSION

DV serodiagnosis will be inconclusive in areas co-endemic for both viruses. The COVID-19 pandemic appears to impart a protective response against DV in DV-endemic populations.

Dengue Infections during COVID-19 Period: Reflection of Reality or Elusive Data Due to Effect of Pandemic

The outbreak of coronavirus disease 2019 (COVID-19) devastated the overall health management strategy of most countries. In this scenario, the present study provided insights into the possible impact of the COVID-19 pandemic on dengue infection. This ecological study retrieved data from WHO/Government reporting system from 22 major dengue epidemic countries. Incidence of dengue infections during the pre-COVID-19 time (2015~2019) and COVID-19 period (2020~2021) was compared. A correlation between the dengue and COVID-19 cases and predicted dengue incidence in 2022 was calculated using the linear regression equation. Data indicated that dengue incidences across the studied area decreased by 16% during the pandemic period (2.73 million vs. 2.29 million; p < 0.05) than the same reported in pre-COVID-19 time. Although countries in Latin America reported more cases than Asia, a positive correlation (r = 0.83) between dengue and COVID-19 cases was observed in Asia. Prediction analysis warned that specific preparation for dengue management is needed in some countries of both regions in 2022 to contain the upsurge in incidences. Due to the similar nature of symptoms of dengue and COVID-19, a state of confusion will be prevailing during the ongoing pandemic. Therefore, comprehensive and evidence-based scientific approaches were warranted at all levels.

Temporal Variations and Spatial Clusters of Dengue in Thailand: Longitudinal Study before and during the Coronavirus Disease (COVID-19) Pandemic

The efforts towards effective control of the COVID-19 pandemic may affect the incidence of dengue. This study aimed to investigate temporal variations and spatial clusters of dengue in Thailand before and during the COVID-19 pandemic. Reported dengue cases before (2011–2019) and during (2020–2021) the COVID-19 pandemic were obtained from the national disease surveillance datasets. The temporal variations were analyzed using graphics, a seasonal trend decomposition procedure based on Loess, and Poisson regression. A seasonal ARIMA model was used to forecast dengue cases. Spatial clusters were investigated using the local indicators of spatial associations (LISA). The cyclic pattern showed that the greatest peak of dengue cases likely changed from every other year to every two or three years. In terms of seasonality, a notable peak was observed in June before the pandemic, which was delayed by one month (July) during the pandemic. The trend for 2011–2021 was relatively stable but dengue incidence decreased dramatically by 7.05% and 157.80% on average in 2020 and 2021, respectively. The forecasted cases in 2020 were slightly lower than the reported cases (2.63% difference), whereas the forecasted cases in 2021 were much higher than the actual cases (163.19% difference). The LISA map indicated 5 to 13 risk areas or hotspots of dengue before the COVID-19 pandemic compared to only 1 risk area during the pandemic. During the COVID-19 pandemic, dengue incidence sharply decreased and was lower than forecasted, and the spatial clusters were much lower than before the pandemic.

Assessing the associations between Aedes larval indices and dengue risk in Kalutara district, Sri Lanka: a hierarchical time series analysis from 2010 to 2019

BACKGROUND

Dengue is a major public health problem in Sri Lanka. Aedes vector surveillance and monitoring of larval indices are routine, long-established public health practices in the country. However, the association between Aedes larval indices and dengue incidence is poorly understood. It is crucial to evaluate lagged effects and threshold values of Aedes larval indices to set pragmatic targets for sustainable vector control interventions.

METHODS

Monthly Aedes larval indices and dengue cases in all 10 Medical Officer of Health (MOH) divisions in Kalutara district were obtained from 2010 to 2019. Using a novel statistical approach, a distributed lag non-linear model and a two-staged hierarchical meta-analysis, we estimated the overall non-linear and delayed effects of the Premise Index (PI), Breteau Index (BI) and Container Index (CI) on dengue incidence in Kalutara district. A set of MOH division-specific variables were evaluated within the same meta-analytical framework to determine their moderator effects on dengue risk. Using generalized additive models, we assessed the utility of Aedes larval indices in predicting dengue incidence.

RESULTS

We found that all three larval indices were associated with dengue risk at a lag of 1 to 2 months. The relationship between PI and dengue was homogeneous across MOH divisions, whereas that with BI and CI was heterogeneous. The threshold values of BI, PI and CI associated with dengue risk were 2, 15 and 45, respectively. All three indices showed a low to moderate accuracy in predicting dengue risk in Kalutara district.

CONCLUSIONS

This study showed the potential of vector surveillance information in Kalutara district in developing a threshold-based, location-specific early warning system with a lead time of 2 months. The estimated thresholds are nonetheless time-bound and may not be universally applicable. Whenever longitudinal vector surveillance data areavailable, the methodological framework we propose here can be used to estimate location-specific Aedes larval index thresholds in any other dengue-endemic setting.

Effects of COVID-19 Non-Pharmacological Interventions on Dengue Infection: A Systematic Review and Meta-Analysis

Non-pharmacological interventions (NPIs) implemented during the coronavirus disease 2019 (COVID-19) pandemic have demonstrated significant positive effects on other communicable diseases. Nevertheless, the response for dengue fever has been mixed. To illustrate the real implications of NPIs on dengue transmission and to determine the effective measures for preventing and controlling dengue, we performed a systematic review and meta-analysis of the available global data to summarize the effects comprehensively. We searched Embase, PubMed, and Web of Science in line with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines from December 31, 2019, to March 30, 2022, for studies of NPI efficacy on dengue infection. We obtained the annual reported dengue cases from highly dengue-endemic countries in 2015–2021 from the European Centre for Disease Prevention and Control to determine the actual change in dengue cases in 2020 and 2021, respectively. A random-effects estimate of the pooled odds was generated with the Mantel-Haenszel method. Between-study heterogeneity was assessed using the inconsistency index (I²) and subgroup analysis according to country (dengue-endemic or non-endemic) was conducted. This review was registered with PROSPERO (CRD42021291487). A total of 17 articles covering 32 countries or regions were included in the review. Meta-analysis estimated a pooled relative risk of 0.39 (95% CI: 0.28–0.55), and subgroup revealed 0.06 (95% CI: 0.02-0.25) and 0.55 (95% CI: 0.44-0.68) in dengue non-endemic areas and dengue-endemic countries, respectively, in 2020. The majority of highly dengue-endemic countries in Asia and Americas reported 0–100% reductions in dengue cases in 2020 compared to previous years, while some countries (4/20) reported a dramatic increase, resulting in an overall increase of 11%. In contrast, there was an obvious reduction in dengue cases in 2021 in almost all countries (18/20) studied, with an overall 40% reduction rate. The overall effectiveness of NPIs on dengue varied with region and time due to multiple factors, but most countries reported significant reductions. Travel-related interventions demonstrated great effectiveness for reducing imported cases of dengue fever. Internal movement restrictions of constantly varying intensity and range are more likely to mitigate the entire level of dengue transmission by reducing the spread of dengue fever between regions within a country, which is useful for developing a more comprehensive and sustainable strategy for preventing and controlling dengue fever in the future.

Water quality characteristics of breeding habitats in relation to the density of Aedes aegypti and Aedes albopictus in domestic settings in Gampaha district of Sri Lanka

In spite of the unavailability of measures to target dengue control in human populations, the promising way of combating the disease is by controlling vector mosquito larvae and their breeding habitats. Water quality characteristics of the breeding habitats of dengue vectors are among the crucial parameters that determine the female mosquito's oviposition and breeding. Therefore, a cross-sectional study was conducted to investigate the habitat characteristics of dengue vector mosquitoes by assessing the water quality of positive breeding habitats using the weighted arithmetic water quality index (WQI). The present study was conducted in domestic areas of the selected medical officer of health areas of the Gampaha district, Sri Lanka, from 2017 to 2019. Water quality characteristics of breeding habituations were measured and analyzed. The relationship between water quality parameters in breeding habitats with the occurrence of mosquito species was assessed using Kruskal-Wallis one-way analysis of variance, followed by pairwise comparison using Dunn's test and Mann-Whitney U test at a 5% level of significance. This study revealed that the temperature of Aedes mosquito breeding water ranged between 25.3 and 39.8 °C, and bred at temperatures as high as 39.8 °C in discarded receptacles. The results indicated that Ae. aegypti was prominent in alkaline water ranging between 7.5 and 8.5 pH, whereas Ae. albopictus was abundant in water with a pH range of 6.5-7.5. Both species of Aedes inhabited waters of low turbidity and TDS level. Ae. aegypti and Ae. albopictus immatures were prominent in water where TDS levels ranged between 250 and 350 ppm. The mean conductivity in the mosquito breeding water was recorded as 228.3 ± 63.9 µs/cm. The study revealed that Aedes mosquitoes could breed in water with a mean dissolved oxygen level of 6.9 ± 0.7 mg/L, ranging between 6.35 ± 1.09 mg/L and 7.28 ± 0.26 mg/L. The water quality indices were calculated for the eight previously identified breeding habitat categories of Aedes mosquitoes.

Measuring the effects of COVID-19-related disruption on dengue transmission in southeast Asia and Latin America: a statistical modelling study

BACKGROUND

The COVID-19 pandemic has resulted in unprecedented disruption to society, which indirectly affects infectious disease dynamics. We aimed to assess the effects of COVID-19-related disruption on dengue, a major expanding acute public health threat, in southeast Asia and Latin America.

METHODS

We assembled data on monthly dengue incidence from WHO weekly reports, climatic data from ERA5, and population variables from WorldPop for 23 countries between January, 2014 and December, 2019 and fit a Bayesian regression model to explain and predict seasonal and multi-year dengue cycles. We compared model predictions with reported dengue data January to December, 2020, and assessed if deviations from projected incidence since March, 2020 are associated with specific public health and social measures (from the Oxford Coronavirus Government Response Tracer database) or human movement behaviours (as measured by Google mobility reports).

FINDINGS

We found a consistent, prolonged decline in dengue incidence across many dengue-endemic regions that began in March, 2020 (2·28 million cases in 2020 vs 4·08 million cases in 2019; a 44·1% decrease). We found a strong association between COVID-19-related disruption (as measured independently by public health and social measures and human movement behaviours) and reduced dengue risk, even after taking into account other drivers of dengue cycles including climatic and host immunity (relative risk 0·01-0·17, p<0·01). Measures related to the closure of schools and reduced time spent in non-residential areas had the strongest evidence of association with reduced dengue risk, but high collinearity between covariates made specific attribution challenging. Overall, we estimate that 0·72 million (95% CI 0·12-1·47) fewer dengue cases occurred in 2020 potentially attributable to COVID-19-related disruption.

INTERPRETATION

In most countries, COVID-19-related disruption led to historically low dengue incidence in 2020. Continuous monitoring of dengue incidence as COVID-19-related restrictions are relaxed will be important and could give new insights into transmission processes and intervention options.

FUNDING

National Key Research and Development Program of China and the Medical Research Council.

Addressing the COVID-19 pandemic challenges for operational adaptations of a cluster randomized controlled trial on dengue vector control in Malaysia

INTRODUCTION

The COVID-19 pandemic placed an unprecedented overload on healthcare system globally. With all medical resources being dedicated to contain the spread of the disease, the pandemic may have impacted the burden of other infectious diseases such as dengue, particularly in countries endemic for dengue fever. Indeed, the co-occurrence of COVID-19 made dengue diagnosis challenging because of some shared clinical manifestations between the two pathogens. Furthermore, the sudden emergence and novelty of this global public health crisis has forced the suspension or slow-down of several research trials due to the lack of sufficient knowledge on how to handle the continuity of research trials during the pandemic. We report on challenges we have faced during the COVID-19 pandemic and measures that were implemented to continue the iDEM project (intervention for Dengue Epidemiology in Malaysia).

METHODS

This randomized controlled trial aims to assess the effectiveness of Integrated Vector Management (IVM) on the incidence of dengue in urban Malaysia by combining: targeted outdoor residual spraying (TORS), deployment of auto-dissemination devices (ADDs), and active community engagement (CE). Our operational activities started on February 10, 2020, a few weeks before the implementation of non-pharmaceutical interventions to contain the spread of COVID-19 in Malaysia.

RESULTS

The three main issues affecting the continuity of the trial were: ensuring the safety of field workers during the interventions; ensuring the planned turnover of TORS application and ADD deployment and services; and maintaining the CE activities as far as possible.

CONCLUSIONS

Even though the pandemic has created monumental challenges, we ensured the safety of field workers by providing complete personal protective equipment and regular COVID-19 testing. Albeit with delay, we maintained the planned interval time between TORS application and ADDs services by overlapping the intervention cycles instead of having them in a sequential scheme. CE activities continued remotely through several channels (e.g., phone calls and text messages). Sustained efforts of the management team, significant involvement of the Malaysian Ministry of Health and a quick and smart adaptation of the trial organisation according to the pandemic situation were the main factors that allowed the successful continuation of our research.

TRIAL REGISTRATION

Trial registration number: ISRCTN-81915073 . Date of registration: 17/04/2020, 'Retrospectively registered'.

Pneumonia, influenza, and dengue cases decreased after the COVID-19 pandemic in Thailand

The coronavirus disease 2019 (COVID-19) pandemic has affected all healthcare systems worldwide. Effective COVID-19 preventive measures, including wearing a mask, hand washing, avoiding the "Three Cs", and city lockdowns, could decrease other infectious diseases. The case numbers of the major infectious diseases in Thailand were investigated (pneumonia, influenza, and dengue fever) during the COVID-19 pandemic using Thailand government national data sources from 2018 to August 2021. Pneumonia, influenza, and dengue fever cases decreased after the COVID-19 pandemic. In addition to respiratory tract infections, COVID-19 preventive measures could decrease dengue fever cases.

The impact of anti‐COVID‐19 non‐pharmaceutical interventions on hand, foot, and mouth disease—a spatiotemporal perspective in Xi'an, northwestern China

Growing evidence has shown that anti‐COVID‐19 nonpharmaceutical interventions (NPIs) can support prevention and control of various infectious diseases, including intestinal diseases. However, most studies focused on the short‐term mitigating impact and neglected the dynamic impact over time. This study is aimed to investigate the dynamic impact of anti‐COVID‐19 NPIs on hand, foot, and mouth disease (HFMD) over time in Xi'an City, northwestern China. Based on the surveillance data of HFMD, meteorological and web search data, Bayesian Structural Time Series model and interrupted time series analysis were performed to quantitatively measure the impact of NPIs in sequent phases with different intensities and to predict the counterfactual number of HFMD cases. From 2013 to 2021, a total number of 172,898 HFMD cases were reported in Xi'an. In 2020, there appeared a significant decrease in HFMD incidence (−94.52%, 95% CI: −97.54% to −81.95%) in the first half of the year and the peak period shifted from June to October by a small margin of 6.74% compared to the previous years of 2013 to 2019. In 2021, the seasonality of HFMD incidence gradually returned to the bimodal temporal variation pattern with a significant average decline of 61.09%. In particular, the impact of NPIs on HFMD was more evident among young children (0–3 years), and the HFMD incidence reported in industrial areas had an unexpected increase of 51.71% in 2020 autumn and winter. Results suggested that both direct and indirect NPIs should be implemented as effective public health measures to reduce infectious disease and improve surveillance strategies, and HFMD incidence in Xi'an experienced a significant rebound to the previous seasonality after a prominent decline influenced by the anti‐COVID‐19 NPIs.

HFMD transmission changed during the COVID‐19 pandemic; The impact of anti‐COVID‐19 NPIs on HFMD varied between different populations; The responsive NPIs indeed affected the HFMD incidence at different stages with potential long‐term impact.

Epidemiological and virological factors determining dengue transmission in Sri Lanka during the COVID-19 pandemic

With the onset of the COVID-19 pandemic in early 2020 there was a drastic reduction in the number of dengue cases in Sri Lanka, with an increase towards the end of 2021. We sought to study the contribution of virological factors, human mobility, school closure and mosquito factors in affecting these changes in dengue transmission in Sri Lanka during this time. To understand the reasons for the differences in the dengue case numbers in 2020 to 2021 compared to previous years, we determined the association between the case numbers in Colombo (which has continuously reported the highest number of cases) with school closures, stringency index, changes in dengue virus (DENV) serotypes and vector densities. There was a 79.4% drop in dengue cases from 2019 to 2020 in Colombo. A significant negative correlation was seen with the number of cases and school closures (Spearman's r = -0.4732, p <0.0001) and a negative correlation, which was not significant, between the stringency index and case numbers (Spearman's r = -0.3755 p = 0.0587). There was no change in the circulating DENV serotypes with DENV2 remaining the most prevalent serotype by early 2022 (65%), similar to the frequencies observed by end of 2019. The Aedes aegypti premise and container indices showed positive but insignificant correlations with dengue case numbers (Spearman r = 0.8827, p = 0.93). Lockdown measures, especially school closures seemed to have had a significant impact on the number of dengue cases, while the vector indices had a limited effect.

Effect of social isolation in dengue cases in the state of Sao Paulo, Brazil: An analysis during the COVID-19 pandemic

BACKGROUND

Studies have shown that human mobility is an important factor in dengue epidemiology. Changes in mobility resulting from COVID-19 pandemic set up a real-life situation to test this hypothesis. Our objective was to evaluate the effect of reduced mobility due to this pandemic in the occurrence of dengue in the state of São Paulo, Brazil.

METHOD

It is an ecological study of time series, developed between January and August 2020. We use the number of confirmed dengue cases and residential mobility, on a daily basis, from secondary information sources. Mobility was represented by the daily percentage variation of residential population isolation, obtained from the Google database. We modeled the relationship between dengue occurrence and social distancing by negative binomial regression, adjusted for seasonality. We represent the social distancing dichotomously (isolation versus no isolation) and consider lag for isolation from the dates of occurrence of dengue.

RESULTS

The risk of dengue decreased around 9.1% (95% CI: 14.2 to 3.7) in the presence of isolation, considering a delay of 20 days between the degree of isolation and the dengue first symptoms.

CONCLUSIONS

We have shown that mobility can play an important role in the epidemiology of dengue and should be considered in surveillance and control activities.

Pandemic-associated mobility restrictions could cause increases in dengue virus transmission

BACKGROUND

The COVID-19 pandemic has induced unprecedented reductions in human mobility and social contacts throughout the world. Because dengue virus (DENV) transmission is strongly driven by human mobility, behavioral changes associated with the pandemic have been hypothesized to impact dengue incidence. By discouraging human contact, COVID-19 control measures have also disrupted dengue vector control interventions, the most effective of which require entry into homes. We sought to investigate how and why dengue incidence could differ under a lockdown scenario with a proportion of the population sheltered at home.

METHODOLOGY & PRINCIPAL FINDINGS

We used an agent-based model with a realistic treatment of human mobility and vector control. We found that a lockdown in which 70% of the population sheltered at home and which occurred in a season when a new serotype invaded could lead to a small average increase in cumulative DENV infections of up to 10%, depending on the time of year lockdown occurred. Lockdown had a more pronounced effect on the spatial distribution of DENV infections, with higher incidence under lockdown in regions with higher mosquito abundance. Transmission was also more focused in homes following lockdown. The proportion of people infected in their own home rose from 54% under normal conditions to 66% under lockdown, and the household secondary attack rate rose from 0.109 to 0.128, a 17% increase. When we considered that lockdown measures could disrupt regular, city-wide vector control campaigns, the increase in incidence was more pronounced than with lockdown alone, especially if lockdown occurred at the optimal time for vector control.

CONCLUSIONS & SIGNIFICANCE

Our results indicate that an unintended outcome of lockdown measures may be to adversely alter the epidemiology of dengue. This observation has important implications for an improved understanding of dengue epidemiology and effective application of dengue vector control. When coordinating public health responses during a syndemic, it is important to monitor multiple infections and understand that an intervention against one disease may exacerbate another.

Characteristics of patients coinfected with Severe Acute Respiratory Syndrome Coronavirus 2 and dengue virus, Lambayeque, Peru, May-August 2020: A retrospective analysis

Introduction

Before the Coronavirus Disease 2019 (COVID-19) arrival and its pandemic, dengue was already a significant cause of epidemics in South East Asia and Latin America. In 2020 with their cocirculation, coinfections began to be observed and reported in different countries. As expected, this syndemic is evident in different areas and deserves proper characterisation and studies in Peru.

Methods

We retrospectively assessed the clinical, epidemiological, diagnostic characteristics and outcomes in a Social Security Hospital of Chiclayo, Lambayeque, Peru, of patients that were diagnosed simultaneously with COVID-19 and dengue during May–August 2020.

Results

A total of 50 patients with COVID-19/dengue coinfection were identified. Of them, 60% presented thrombocytopenia, and 52% fever, among other findings. The case fatality rate in this group was 28%, being higher in those patients initially classified as severe dengue (100%), as well as in females (55%) than males (21%) (OR = 4.65; 95%CI 1.18–18.45).

Discussion

Co-occurrence of COVID-19/Dengue is growing as a consequence of the syndemic of these viral diseases in endemic areas, such as Latin America, and as both conditions may evolve to severe disease, their epidemiological but clinical interaction in terms of outcomes need further assessment in future studies in the region.