Effects of West Nile Virus May Linger
West Nile Virus Infection Affects Brain in Some
July 22, 2003 -- Infection with West Nile virus not only may cause short-term illness, but it also may have lingering effects on the brain in a small number of people.
A new study published in The Journal of the American Medical Association shows long-term neurological effects such as headaches, memory loss, movement disorders, and muscle aches are common among people infected with West Nile virus, and partial paralysis also may develop in a small number of people.
Researchers say less than 1% of people infected with West Nile virus develop a serious brain inflammation illness known as viral encephalitis and most develop only a mild fever or flu-like condition.
Although recent West Nile outbreaks have been associated with severe neurological disease, researchers say until now there haven't been any long-term studies to examine whether encephalitis caused by West Nile virus is any different than other types of viral encephalitis or whether it has any lasting effects.
Initial Effects of West Nile Virus
In this study, CDC researchers analyzed 39 suspected cases of West Nile infection in Louisiana from August 1 to September 2, 2002 as they were reported and re-evaluated them after eight months. They found:
- Sixteen developed antibodies to the West Nile virus.
- Five had meningitis, inflammation of tissue that surrounds that brain and spinal cord.
- Eight had encephalitis, inflammation of the brain.
- Three had a polio-like paralysis and lack of muscle function.
- One patient died.
Movement disorders such as tremors, sustained muscle contractions, and Parkinson's disease-like conditions were also common among the 16 who tested positive for antibodies to the West Nile virus.
After eight months of follow-up, researchers found patients with meningitis or viral encephalitis had favorable outcomes, but those who suffered from paralysis did not recover muscle or limb strength.
In addition, complaints of fatigue, headache, and muscle aches were frequent, and gait and other muscle disorders persisted in six patients.
Researcher James J. Sejvar, MD, of the CDC, and colleagues say movement disorders may be underrecognized effects of serious West Nile virus-related illness, but generally improve over time.
However, over the long term, they say the outcome of West Nile virus infection is variable, and severe viral encephalitis at the start does not necessarily mean a poorer prognosis. But loss of muscle function or paralysis associated with West Nile infection may occur without other illnesses and have serious lasting effects.