Large trial to identify the long-term health effects of West Nile virus infection

May 18 2007

UT Southwestern Medical Center has joined a national clinical trial to identify the long-term health effects of West Nile virus infection and to learn more about the disease's progression, symptoms and mortality.

In the trial, initiated by the National Institutes of Health Clinical Center, researchers at 13 U.S. sites are observing the natural course of the virus over a year in people who have either a fever or neurological diseases due to West Nile infection.

Study participants undergo brain imaging and blood, neurological and cognitive testing.

“Little is known about the long-term effects of infection, so information gathered in this trial could help bridge the gaps in current knowledge of West Nile and aid in the design of better treatments,” said Dr. Roger Bedimo, assistant professor of internal medicine at UT Southwestern and chief of infectious disease at the Veterans Administration North Texas Health Care System. Dr. Bedimo is principal investigator of the trial site at UT Southwestern.

West Nile virus, transmitted by mosquito bite, arrived in the U.S. in 1999 and has become a seasonal illness that flares up between May and October. The young, the elderly and people with weak immune systems are most at risk.

About 7 percent of all U.S. cases of West Nile appear in Texas each year. Last year, 23 percent – or 81 cases – of Texas' 354 verified human infections were in Dallas County.

West Nile virus infection has three main forms. Most people have no symptoms and their immune system clears out the virus. One in 5 people develops a fever – West Nile Fever – that causes mild flu-like symptoms. One in 150 develops serious neurological illness, such as severe headache, muscle weakness, cognitive impairment, coma, seizures and encephalitis and myelitis.

Since there is no vaccine, doctors can only treat symptoms of the disease.

Several researchers at UT Southwestern, including Dr. Michael Gale, associate professor of microbiology, are studying at the molecular level how the disease evades the body's immune defenses in hopes of finding a vaccine to protect against the harmful North American strain of the West Nile virus.

For now, avoiding mosquito bites is the best prevention. Physicians recommend wearing insect repellant that contains the chemical DEET when people go outdoors. Also keep doors, window screens and tents in good repair, and get rid of standing water – prime mosquito breeding grounds – around the house.

Diagnosing a typical case of West Nile involves testing for antibodies in the blood. In a case involving neurological disease, a diagnosis involves a spinal tap. Positive cases are reported locally to the Dallas County Department of Health and Human Services.

For this current trial, UT Southwestern will be seeking participants who have been diagnosed by their primary-care physician in outpatient clinics and those admitted to UT Southwestern University Hospital, Parkland Memorial Hospital or the Dallas VA medical center. Patients must be at least 18 to be enrolled, and other inclusion and exclusion criteria apply. After an initial evaluation, participants would be evaluated five more times over a year.

“There are many concerns as to what the long-term consequences of West Nile virus infection are, so we want to shed light on this,” Dr. Bedimo said.