West Nile fever is not simply a 3- to 6-day disease with limited symptoms, but rather a severe illness that can incapacitate people for a month or longer, findings from a new study indicate.

“We found that West Nile fever was quite a bit more severe than had previously been recognized,” lead author Dr. John T. Watson, from the Chicago Department of Public Health, told Reuters Health. The typical time needed “for patients to get back to a point considered normal was 60 days and about a third of patients required hospitalization.”

The findings, which appear in the Annals of Internal Medicine, are based on a survey of 98 patients who survived a 2002 outbreak of West Nile virus infection in Illinois. All of the subjects had lab tests confirming their infection, but none had symptoms of encephalitis, a serious but rare type of brain inflammation that can occur.

Although the duration of fever was typically just 5 days, other symptoms persisted for much longer. For example, fatigue, headache, muscle weakness, and difficulty concentrating were all common symptoms that lasted for about 36, 10, 28, and 14 days, respectively. Sixty-three percent of subjects still reported symptoms 30 days after becoming infected.

Thirty patients required hospitalization and the usual length of stay was 5 days, the investigators note. Of the 72 subjects who reported regular work or school attendance, 57 missed around 10 days because of their illness.

West Nile fever is a more debilitating disease than we expected, Watson said. “I think our findings are useful to (doctors) in advising patients what to expect with West Nile fever.”

SOURCE: Annals of Internal Medicine, September 7, 2004.