WASHINGTON Patients infected with West Nile virus can develop long-term symptoms such as fatigue, fuzzy thinking and movement difficulties but these symptoms go away after about a year, doctors reported on Monday.
The mosquito-borne virus arrived in the Americas in 1999 and quickly began to sicken patients in New York. It has now spread across the United States, Canada and Mexico and continues to infect people in Africa, Australia, western Asia, Europe and the Middle East.
West Nile causes no symptoms in about 80 percent of cases. About one in 150 people infected with the virus develop severe illness with high fever, headache, neck stiffness, stupor, disorientation, vision loss, numbness, coma, paralysis and other symptoms.
Sometimes the neurological effects last for weeks or months and many doctors had feared this nerve damage was permanent.
Dr. Mark Loeb of McMaster University in Ontario, Canada, and colleagues wanted to see what the long-term effects were.
"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," Loeb said in a statement.
"We found that both physical and mental functions, as well as mood and fatigue, seemed to return to normal in about one year."
Writing in the Annals of Internal Medicine, Loeb said his team studied 156 West Nile patients between 2003 and 2007.
They found symptoms and recovery times were similar among patients who had neurological effects and those who did not.
There is no human vaccine for West Nile virus, although one is sold to protect horses. The U.S. Centers for Disease Control and Prevention advises people to use repellents containing DEET and clothing to cover up as the best way to prevent mosquito bites and infection.
(Reporting by Maggie Fox; editing by Mohammad Zargham)