Good long-term prognosis after West Nile virus infection

The long-term prognosis of patients infected with West Nile virus is good, according to a new study appearing in the August 19, 2008, issue of Annals of Internal Medicine, the American College of Physicians' flagship journal. This is the largest study of the long-term outcomes of 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.

Annals of Internal Medicine (www.annals.org) is one of the five most widely cited peer-reviewed medical journals in the world. The journal has been published for 81 years and accepts only seven percent of the original research studies submitted for publication. Annals of Internal Medicine is published by the American College of Physicians (www.acponline.org), the largest medical specialty organization and the second-largest physician group in the United States. ACP members include 126,000 internal medicine physicians (internists), related subspecialists, and medical students. Internists specialize in the prevention, detection, and treatment of illness in adults.