Ill Effects of West Nile Infection May Linger

NEW YORK (Reuters Health) – More than a year after being diagnosed with a West Nile virus infection, nearly half of the patients have ongoing health issues including fatigue, memory problems, headache, depression and tremor, a new study shows.

The study also warns that patients diagnosed with West Nile fever, which has generally been thought to be a relatively benign, self-limited condition, are just as likely to have lingering health issues as patients who develop more severe West Nile virus-related illnesses such as encephalitis or meningitis.

“I hope this study will raise awareness that West Nile virus poses a substantial public health threat,” Dr. Paul J. Carson, of MeritCare Health System in Fargo, North Dakota, who led the research effort, said in a statement from the Infectious Disease Society of America. Carson’s research is published in the IDSA journal Clinical Infectious Diseases.

“We knew before that West Nile encephalitis was a serious health threat, but we didn’t appreciate how much ongoing morbidity there is for West Nile fever, which is much more common,” he said.

West Nile virus is spread to humans by infected mosquitoes. The virus first surfaced in the United States in 1999. In 2003, there were more than 9,000 human cases of West Nile virus-related disease, including 264 deaths.

Most people infected with West Nile virus have no symptoms. However, roughly 20 percent will develop a flu-like illness called West Nile fever. Up to 1 percent may develop more severe diseases such as meningitis or encephalitis.

Carson and colleagues assessed the health of 38 patients with West Nile fever and 11 with West Nile meningitis or encephalitis roughly 13 months after being diagnosed.

“Self-reported fatigue, memory problems, extremity weakness, word-finding difficulty, and headache were common complaints,” according to the team. Further investigation revealed an overall sense of poor physical health and fatigue in 24 patients (49 percent), depression in 12 (24 percent), and moderate-to-severe disability in 4 (8 percent).

New tremor was seen or reported in 10 patients (20 percent); neurological and psychological testing revealed abnormalities of motor skills, attention and executive functions.

It’s noteworthy, according to the team, that patients with milder West Nile illness were just as likely as those with more severe West Nile illness to experience these health problems.

Carson hopes these results “may give greater impetus to increase resources for prevention — vector control and vaccine — and treatment development.”

SOURCE: Clinical Infectious Diseases September 15, 2006.

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