Mosquito-borne diseases
West Nile Virus Overview
West Nile virus (WNV) is a mosquito-borne virus in the Flavivirus genus of the Flaviviridae family. It is naturally transmitted between mosquitoes and birds, but humans, horses, and other animals can also contract it. Most infections in humans are asymptomatic, but some develop West Nile fever, a mild illness with fever and fatigue. In rare instances, less than 1% of cases, the virus can cause severe neurological issues like meningitis or encephalitis. History and Global Spread WNV was initially discovered in 1937 in the West Nile area of Uganda. Over the years, it spread throughout Africa, the Middle East, and Europe. In 1999, the virus was detected in the United States for the first time, starting an outbreak in New York City. It quickly spread, becoming endemic across North America. Transmission Cycle In North America, the virus primarily spreads through bites from infected Culex mosquitoes, particularly Culex pipiens, Culex quinquefasciatus, and Culex tarsalis. Birds act as the main hosts that magnify the virus, whereas humans and horses are “dead-end” hosts because they do not reach sufficient viral levels to infect mosquitoes. The risk of transmission rises in late spring, summer, and early fall when mosquito activity peaks. Older adults and those with weakened immune systems are at higher risk for severe illness. Symptoms and Health Impact While most infections are asymptomatic, approximately 20% of individuals experience flu-like symptoms like fever, headache, and body aches. A small portion of cases can develop into neuroinvasive disease, potentially leading to long-term neurological issues. Challenges in Modeling WNV Transmission Predicting and understanding WNV outbreaks is challenging because of the virus’s complex ecological cycle. Its transmission involves interactions between mosquitoes, birds, and incidental hosts, forming feedback loops that complicate mathematical modeling. Modeling efforts are further hindered by uncertainties in ecological and epidemiological parameters, gaps in surveillance data, environmental variability, particularly temperature and rainfall, and the effects of climate change on vector populations and viral replication. Achieving accurate forecasts depends on integrating real-time environmental, vector, and host data, a capability that only a few current modeling systems possess. The Role of the FloDisMod Project The FloDisMod project tackles these issues by collaborating with health departments across various cities and counties to improve real-time risk modeling for West Nile virus. Working with local mosquito control districts, public health offices, and environmental agencies, the project integrates field-collected data, including mosquito trap counts, bird infection reports, and habitat assessments, into its models. These partnerships help ensure that predictions accurately capture biological complexities and reflect local operational conditions. By combining sophisticated modeling with community expertise, FloDisMod helps public health officials make timely, informed decisions on mosquito control, public communication, and targeted actions during peak risk periods
- WHO: ttps://www.who.int/news-room/fact-sheets/detail/west-nile-virus
- CDC: https://www.cdc.gov/west-nile-virus/hcp/clinical-signs/index.html
- VDCI: https://www.vdci.net/blog/2025-mosquito-borne-disease-year-in-review/