West Nile Virus

West Nile virus (WNV), is a disease transmitted to humans, birds, horses, and other animals, by infected mosquitoes. Mosquitoes get the disease from infected birds while taking blood and can later pass it on when they bite animals or humans.

WNV is established in Sacramento and Yolo counties and can be found in all 58 counties in California! The virus was first isolated in the West Nile district of a Northern Province in Uganda in 1937. It was first detected in the United States in New York City in 1999. From there, the virus spread westward, arriving in California in 2003. West Nile virus is now the most prevalent mosquito-borne disease in the United States.

The majority of individuals (roughly 80%) who are bitten by an infected mosquito will show no symptoms. Roughly 20% of infected individuals develop West Nile Fever. Symptoms often mimic typical flu symptoms including:
• Fever
• Headache
• Fatigue
• Occasional skin rash
• Eye pain or swollen lymph glands

The symptoms of West Nile Fever may last two to three weeks with an uneventful recovery or the disease may progress to a severe disease in roughly 1% of individuals. Severe symptoms may include fever, seizures, weakness, change in mental status, paralysis and death.

Anyone who receives a bite from a mosquito infected with West Nile virus is at risk but two factors put individuals at greater risk of becoming ill—mosquito exposure and personal characteristics.

Being outdoors increases exposure to infected mosquitoes. Therefore, the more time spent outside, the greater the chance of contracting West Nile virus.

Personal characteristics may also place people at greater risk. Factors such as age, health, immune system, high blood pressure, diabetes, and more can make an individual more susceptible to the virus.