Source: Centers for Disease Control and Prevention — Content from the Centers for Disease Control and Prevention (public domain).
About Mosquitoes spread West Nile virus. Illness ranges from mild to severe. June 16, 2026 
Prevention Protect yourself and your family from mosquito bites to prevent West Nile virus. Sept 8, 2025 Symptoms Symptoms of West Nile include fever, head and body aches, and more. Illness can be severe. Causes and Spread Infected mosquitoes spread West Nile virus throughout the United States. Data and Maps for West Nile West Nile cases occur nationwide. State and territorial health departments report case data. For Professionals 
Treatment and Prevention Treatment is supportive. Patients with encephalitis or acute flaccid myelitis require monitoring. Aug 19, 2025 
Clinical Signs and Symptoms West Nile can present as acute febrile or neurologic illness after exposure to mosquitoes. Aug 19, 2025
* Clinical Testing and Diagnosis Test patients’ serum or cerebrospinal fluid for West Nile virus. Additional testing may be needed.
* Transmission West Nile cycles between mosquitoes and birds. Other modes of transmission occur rarely.
* West Nile Virus Resources CDC publishes guidelines, scientific reports, and other resources on West Nile virus.
* WNV Clinician Training Learn how to diagnose and manage West Nile virus disease.
* Outbreak Communications Toolkit Health departments can use a CDC-created toolkit to communicate about West Nile outbreaks.