West Nile virus, spread by mosquitoes, has shown up in nearly every state since it was first introduced into the United States in 1999. In 2003, 2,866 people fell ill and 264 died. During the late summer and early fall, when people are most likely to become infected, a good deal of the information is focused on prevention. But scientists from New York City's Department of Health and the Centers for Disease Control and Prevention put out an August report on the long-term effects of West Nile infection.

What they wanted to know: How well were patients doing a year and a half after being infected with West Nile virus and what contributed to their recovery?

What they did: The researchers interviewed about 30 of the 59 people who survived being hospitalized because of West Nile virus in 1999 in New York City. Six months, 12 months, and 18 months after being infected, the participants answered questions about their physical, mental, and functional health such as whether or not they had trouble walking, whether they often felt confused, and whether they could complete tasks such as cleaning the house or doing the laundry.

What they found: More than half the patients, 63 percent, did not achieve full recovery a year after being infected. Many still had symptoms after 18 months, and more than half said they often felt tired, had muscle weakness, and had difficulty doing heavy chores. Slightly less than half felt depressed, lightheaded, and irritable after 18 months. Age was the only predictor of a faster recovery time, with younger people about three times as likely to achieve full recovery than older participants.

What it means to you: West Nile can be a very debilitating disease. Still, 80 percent of the people who are infected never develop any symptoms and less than 1 percent become severely ill. People with weak immune systems, such as the elderly, are at an increased risk and should protect themselves by wearing mosquito repellent when they are outdoors. It's not a bad idea for everyone to protect themselves with bug repellent (and it'll keep you from spending the next week itching), but West Nile shouldn't keep you from enjoying the outdoors.

Caveats: Only about 30 people, all living in New York City, participated in this study, making it hard to generalize the data to the entire country. In addition, the age of the participants ranged from 16 to 90 years old, so it is hard to see how age affected recovery when there were so few people in each age group. Also, participants' recovery was judged against how well they remembered their health before getting West Nile, and the interviews about their prior health did not take place until a year after they had been infected, and poor memory could have skewed the data.

Find out more: The Centers for Disease Control and Prevention has a lot of information on West Nile, including its prevalence and how to prevent it.

For information on the little buggers that carry the disease, the Rutgers University website has a nice description of mosquitoes complete with films showing various mosquitos.

And, unfortunately, you've probably missed this year's mosquito festival in Paisley, Ore. But if you want to get a jump on next year, the festival has a website: http://paisley.presys.com/

Read the article: Klee, A.L. et al. "Long-Term Prognosis for Clinical West Nile Virus Infection. Emerging Infectious Diseases." August 2004, Vol. 10, No. 8, pp. 1405–1411.

Article online: http://www.cdc.gov/