How did West Nile virus rates change in 2021 compared to the previous decade?
West Nile virus is the leading cause of domestically acquired arboviral disease in the continental United States 1. While cases typically peak between April and September 1, the overall number of infections has been rising. Specifically, 2021 saw higher rates than the average for the previous decade 3.
What the research says
A surveillance report from 2021 explicitly describes increased rates of West Nile virus in the U.S. compared to the median rate observed during the 2010-2020 period 3. This rise occurred despite a decrease in neuroinvasive disease specifically in 2019 7. The increase in 2021 was significant enough to be highlighted as a distinct trend compared to the prior ten years 3.
Other factors contribute to these changing rates. A 2024 study notes that the incidence of West Nile virus, including its neuroinvasive form, is increasing largely due to the expanding distribution of the Culex mosquito and climatic changes like heavy monsoon rains 8. Additionally, a 2023 study in Germany found that while minimum infection rates remained low, the intensity of virus circulation appeared to be increasing compared to previous studies 10.
What to ask your doctor
- How do local climate patterns or mosquito populations in my area affect my risk for West Nile virus?
- What are the current surveillance trends for West Nile virus in my state compared to the national median?
- Are there specific symptoms I should watch for if I am exposed to mosquitoes during the summer months?
- What steps can I take to reduce my risk of infection given the increasing rates reported recently?
This question is drawn from common patient questions about Infectious Disease and answered using cited medical research. We do not provide individualized advice.