COVID-19 Pandemic Disrupted Dengue Transmission

The COVID-19 pandemic is often examined in the context of "bench to bedside" medical breakthroughs, morbidity and mortality, or displacement and disruption. The later underlie recently published findings that link the pandemic to historically low dengue incidence in southeast Asia and Latin America.

Yuyang Chen, PhD, State Key Laboratory of Remote Sensing Science, Center for Global Cha nge and Public Health, College of Global Change and Earth System Science, Beijing, China, and colleagues attribute an approximate 35% decrease in dengue cases to the social-behavioral restrictions imposed to curtail the COVID-19 pandemic.

"By combining the most globally comprehensive collection of dengue and COVID-19 response data, we show that the sudden decline in dengue cases in April, 2020 is associated with the imposition of restrictions and changes in human movement behaviors," Chen and colleagues declared.

To build a model to predict the dengue cases in 23 countries (16 in Latin America and 7 in southeast Asia) that would have been expected to occur between January and December 2020 in absence of a pandemic, and to obtain the actual incidence, the investigators sourced data from WHO weekly reports from 2014-2020. Recognizing the mosquito as a vector for the disease, they also collected environmental data from ERA5 (European Center for Medium Range Weather Forecasting v5) including air temperature at 2m above the earth's surface, surface temperature, relative humidity, convective and total precipitation.

Data on public health and social measures imposed in response to the COVID-19 pandemic were extracted from the Oxford Coronavirus Government Response Tracer (OxCGRT) project.These included 8 categories of containment and closure measures, as well as overall stringency index values

In invited commentary accompanying the published study, Tedjo Sasmono, PhD, and Marsha Santoso, MIPH, MD, Eijkman Institute for Molecular Biology, National Research and Innovation Agency, Jakarta, Indonesia, welcomed this approach, which they posit could provide new insights on potential interventions.

"The intensity levels and forms of mobility restrictions varied geographically across different countries and temporally throughout the months of 2020, providing a unique opportunity to analyze these variables in how the affect transmission in infectious diseases other than COVID-19, such as dengue," Sasmono and Santoso indicated.

Applying Bayesian regression models to the data on incidence, climacticand population variables, Chen and colleagues estimated that there were an approximate 0.72 million fewer cases (95% CI 0.12-1.47) between April and December 2020 in the study areas than would have occurred absent the pandemic.This represented a 35% (9-56) decrease, which they indicate is potentially attributable to COVID-19 related disruption.

The restriction with the strongest association with reduction in cases were school closures and reduced time spent in non-residential areas. Although the investigators caution against "over interpretation," they nevertheless note that the mosquito vector, Aedes aegypti, preferentially bites during the day, and suggest that schools and other commonly visited public areas could be dengue transmission hotspots.

"If supported by further outbreak investigation studies, this finding suggest a greater emphasis is needed on dengue control in public places, and in schools in particular," Chen and colleagues indicate.

Sasmono and Santoso agree, and point out that while implementing policies that restrict community mobility have proved challenging, "options to focus vector control interventions to more public areas could be potential alternatives."

As with the beneficial, but short-lived reduction in fossil fuel emissions corresponding tothe pandemic disruption of industry and transportation, Chen and colleagues anticipate that the reduction in dengue incidence will also prove transitory as the restrictions imposed for the pandemic are lifted.

"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," they advised.