Symptoms of West Nile virus infection may persist

By Megan Rauscher

NEW YORK (Reuters Health) - Infection with mosquito-borne West Nile virus (WNV) can result in significant long-term problems, such as mental and functional impairment, as well as depression, according to data from an ongoing study funded by the National Institutes of Health presented Monday at the International Conference on Emerging Infectious Diseases in Atlanta.

"People who have the greatest sequelae are those (who) had the most severe form of the disease, which is encephalitis," lead investigator Dr. Kristy O. Murray from University of Texas Health Science Center at Houston noted in a telephone interview with Reuters Health ahead of the meeting. "Seventy-seven percent of those with encephalitis have persistent neurologic exams that are abnormal."

Murray presented data from 108 patients infected with WNV in the Houston area in 2002. Thus far, the patients have been evaluated every 6 months for up to 5 years. Fifty-four patients (50 percent) presented with encephalitis, 32 (30 percent) with meningitis and 22 (20 percent) with uncomplicated fever.

Persistent symptoms from WNV infection were reported by roughly 60 percent of the group 1 year after infection, Murray reported. Five years after infection, 42 percent of subjects still had symptoms related to WNV.

"What we are finding," Murray said, "is that the first 2 years are the most important in terms of recovery. Most of the recovery is going to happen within that time. Recovery plateaus at about 2 years. I haven't seen anyone after 2 years improve in their symptoms. They continue to experience whatever long-term sequelae that they have."

The most commonly reported symptoms include fatigue, weakness, depression, personality changes, difficulty walking, memory deficits and blurred vision.

"Depression is a very important outcome we are finding," Murray emphasized. About 31 percent of patients said they became depressed after WNV infection and, using objective measures, the researchers determined that 75 percent of those cases met the definition of clinical depression.

"This study, Murray and colleagues wrote in a meeting abstract, "provides us with a better understanding of the clinical aspects of a virus that is likely to continue to be an important global emerging pathogen."