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. Author summary Dengue virus causes substantial suffering in the tropical and subtropical regions of the world, with roughly 400 million infections and 40,000 deaths each year. In 2020, we witnessed unprecedented changes in human movement as the world tried to combat the COVID-19 pandemic, including in countries that regularly experience dengue epidemics, such as Thailand and Peru. These changes could affect transmission of dengue virus, though it is unclear whether transmission will decrease, as people reduce their movements between houses, or increase, as people spend more time at home and campaigns to control the mosquito vector of dengue virus are interrupted. We used a simulation model to estimate the impact of these changes on dengue virus transmission. Our model describes the locations of buildings and the movement of people between them, allowing us to directly estimate what happens when human movement patterns change. We found that as people spend more time at home, transmission is likely to increase moderately. If these changes also lead to disruption to vector control, the magnitude of the increase is greater. Our results reinforce concerns about the complexity of public health responses to multiple overlapping epidemics and support the need for policy makers and health authorities to think holistically in their intervention planning.

Automated summary

The COVID-19 pandemic-induced lockdown measures and disruption of vector control interventions may lead to an increase in dengue incidence. Coordination of public health responses considering multiple overlapping epidemics is important for effective intervention planning.