West Nile Virus

West Nile Virus maintains itself in a bird-mosquito transmission cycle. Culex mosquitoes feed on infected birds, amplify the virus in their salivary glands, and then transmit it to humans as a "dead end host" — humans don't develop high enough viral loads to infect other mosquitoes, so the cycle doesn't continue through us.

Crow and jay deaths as warning signs: Mass deaths of crows, jays, ravens, and other corvids are early indicators of West Nile Virus circulating in an area. Report dead bird clusters to your local health department — this data is used to track geographic spread.

Peak transmission season: July through September in most of the U.S. — when Culex mosquito populations peak and temperatures are high enough for rapid virus replication inside the mosquito.

Risk by geography: Cases are reported in all 48 contiguous states. The highest recent burden has been in California, Texas, Arizona, and the central plains states — but risk exists wherever Culex mosquitoes are present.

Symptom spectrum: 80% of infected people experience no symptoms. About 20% develop West Nile Fever — headache, body aches, fever, fatigue, skin rash. This resolves on its own in days to weeks. Less than 1% develop neuroinvasive disease: encephalitis (brain inflammation), meningitis (meningeal inflammation), or acute flaccid paralysis. Neuroinvasive disease can be severe and occasionally fatal.

High-risk groups: Adults over 60 and immunocompromised individuals face significantly higher risk of severe neuroinvasive disease. These groups should be especially diligent about mosquito bite prevention.

Prevention protocol: DEET 25–30% or Picaridin 20% applied to exposed skin during dusk and dawn hours. Long sleeves and pants during peak Culex feeding times. Eliminate standing water weekly — Culex mosquitoes breed in stagnant, warm water with organic matter. Window and door screens in good repair. Bti dunks for water that can't be drained.