McMaster University

McMaster University

Faculty of
Health Sciences

West Nile Virus — patients recover after one year

By Laura Thompson
Published: August 18, 2008
Mark Loeb
Dr. Mark Loeb, a professor of Pathology and Molecular Medicine in the Michael G. DeGroote School of Medicine.

People infected with West Nile virus seem to return to normal within one year of experiencing symptoms, a new McMaster study has found.

The study, published today in the Annals of Internal Medicine, is the largest ever done on the long-term prognosis of West Nile virus.

"This is the first study to comprehensively look at a large population of infected persons to study the long-term effects of West Nile virus," said study author Dr. Mark Loeb, a professor of Pathology and Molecular Medicine in the Michael G. DeGroote School of Medicine.

West Nile virus is a potentially serious central nervous system infection transmitted by mosquitoes. The disease can be difficult to diagnose because most people infected do not get sick. However, 20 per cent have symptoms that range from mild flu-like sickness to neurological problems such as inflammation of the brain or acute flaccid paralysis, which is the sudden onset of limb weakness.

McMaster researchers followed 156 patients between 2003 and 2007 to record patterns of physical and mental effects of West Nile virus infection. They also recorded if participants experienced depression and fatigue. Researchers anticipated greater severity and a longer course of depression and fatigue in participants with neurological problems. However, they found symptoms and recovery times to be similar to those in participants without neurological complications.

"What it means is that if you’ve had West Nile virus infection — meningitis or encephalitis or just West Nile fever — on average, over a year, you will normalize in terms of the specific functions that we looked at," Dr. Loeb said.

In addition, the study found that patients who were healthy at the time of infection returned to normal health more quickly on average than those who had pre-existing conditions.

Researchers say the study will help West Nile patients and their doctors know what to expect in terms of the rate of recovery of physical and mental functioning, fatigue and depression.

The Annals of Internal Medicine is published by the American College of Physicians.

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