According to the CDC and the National Library of Medicine, symptoms of West Nile Virus can be asymptomatic, or can lead to West Nile fever or severe West Nile disease which show symptoms similar to those of other viral infections. The most common symptom is a rash, which effects up to half of patients infected with West Nile Virus. Most people (about 4 out of 5) who are infected with West Nile virus will not develop any type of illness (an asymptomatic infection).
About 20% of people infected with West Nile Virus will develop mild disease, generally called West Nile Fever. Symptoms of West Nile fever include:
- Abdominal pain
- Body Aches
- Rash (trunk of body)
- Lack of appetite
- Sore throat
- Swollen lymph nodes
- Muscle aches
These symptoms usually last for 3 - 6 days. While the illness can be as short as a few days, even healthy people have reported being sick for several weeks.
Severe versions of West Nile disease including West Nile encephalitis, West Nile meningitis, or West Nile poliomyelitis depending on what part of the body if affected need immediate attention. Symptoms of severe disease include:
- High fever
- Neck stiffness
- Confusion/stupor/disorientation or change in ability to think clearly
- Loss of consciousness or coma
- Muscle weakness
- Weakness of one arm or leg
The CDC estimates that 1 in 150 persons infected with West Nile Virus will develop a more severe form of the disease. Serious illness can occur in people of any age but people over the age of 50 and immunocompromised persons are the most at risk.