Good Long-term Prognosis After West Nile Virus Infection

West Nile virus is a potentially serious central nervous system infection spread by mosquitoes. Many people infected by West Nile virus never get sick, so the disease can be difficult to diagnose. However, approximately 20 percent have symptoms that range from mild flu-like illness to neurological problems such as meningoencephalitis, encephalitis, and acute flaccid paralysis. Recent studies report that troublesome symptoms such as fatigue, cognitive dysfunction, and motor abnormalities can persist for months. However, little is known about long-term recovery.

"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 Mark Loeb, MD, MSc, Professor, Pathology and Molecular Medicine, Michael G. DeGroote School of Medicine, McMaster University, Ontario, Canada. "We found that both physical and mental functions, as well as mood and fatigue, seemed to return to normal in about one year."

Researchers followed 156 patients between 2003 and 2007 to record patterns of physical and mental effects of West Nile virus infection. 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 consequences of infection. Pre-existing health conditions were an important factor in long-term prognosis. 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 data might help patients infected with West Nile virus and their health care providers know the expected rate of recovery of physical and mental functioning, fatigue, and depression.