Connecting Earth Observations with Public Health Surveillance to Predict Mosquito-Borne Disease Outbreaks Based on Environmental Variations

Climate variations have a multitude of effects on infectious disease transmission arising from their influences on pathogens, arthropod vectors, and zoonotic hosts. In particular, extreme weather conditions such as heat waves, droughts, and floods lead to major ecological changes that can either interrupt transmission or lead to unprecedented disease outbreaks. Infectious disease surveillance has traditionally focused on tracking human cases along with the abundances and infection status of vectors and hosts. For climate-sensitive diseases, surveillance can be strengthened by monitoring environmental risk factors using broad-scale sensor networks that include earth-observing satellites as well as ground stations. We explored the effects of extreme environmental conditions on mosquito-borne disease outbreaks using data from two projects focused on surveillance and forecasting of mosquito-borne diseases. The Epidemic Prognosis Incorporating Disease and Environmental Monitoring for Integrated Assessment (EPIDEMIA) project integrates malaria case surveillance with remotely-sensed environmental data for early detection of malaria epidemics in the Amhara region of Ethiopia. The Arbovirus Modeling and Prediction (ArboMAP) project combines entomological surveillance with gridded meteorological data to generate weekly risk maps for West Nile virus (WNV). ArboMAP is used to make weekly forecasts for South Dakota, the U.S. state with the highest long-term incidence of WNV. Despite important differences in disease ecology and geographic setting, there was a strong influence of positive temperature anomalies on the probability of disease outbreaks for both malaria and West Nile virus. However, these effects were contingent on the seasonal timing of temperature fluctuations and varied depending on local climatic conditions, land use and land cover, and public health interventions. The influences of moisture-related anomalies, including precipitation and humidity, were generally weaker and more geographically variable. These results suggest the possibility of a generalizable effect of warmer-than-normal temperatures on mosquito-borne diseases in temperate and highland tropical settings. However, these effects will also be sensitive to a variety of localized physical, biological, and social contingencies.