The future of West Nile and Even as virus is entrenched in nation, mysteries remain
Since West Nile's first U.S. appearance, researchers have learned more about the virus but there are still unknowns.
• Six years later, mysteries remain
• A North American fixture
• The animal connection
• Diseases beyond West Nile
I felt exhausted, but she blamed it on recent travel. Then came the nausea. Four days later, the 67-year-old lay comatose in intensive care, battling encephalitis caused by West Nile virus.

"I feel ignorant because I hadn't paid attention and I didn't know anything about it," said the Phoenix, Arizona, resident. "I never gave it a thought."

After more than six weeks in the hospital starting in June 2004, Thrower has spent the last year recovering at home. She still suffers from fatigue, muscle and joint problems and a weakened immune system.

"It's affected my whole life. Things that I did before I can't do," she said. "I was a substitute teacher and I couldn't do that this past year."

Thrower is one of the more than 16,000 U.S. cases of West Nile virus since it first appeared in the country in 1999. Six years and more than 600 deaths later as the frenzy dwindles, health officials say West Nile is not disappearing any time soon and they are beginning to uncover some new mysteries about the illness.

"There's still a lot of activity out there in many parts of the country and there's no reason to think it's just going to go away from various places because it really hasn't ever done that," said John Roehrig, who studies West Nile as chief of the U.S. Centers for Disease Control and Prevention's arbovirus diseases branch in Fort Collins, Colorado. "In all the states that have had West Nile, they've maintained some level of activity for West Nile."

In 2004, human cases in the United States dipped to 2,470 with 88 deaths after previous years of big increases. Cases in 2003, for example, numbered nearly 10,000 with 264 deaths. But whether the downward trend will continue this season and into the future is still an unknown, according to researchers.

Some believe West Nile may take on a cyclical pattern, similar to its virus cousin, St. Louis encephalitis, another illness transmitted by mosquitoes that causes inflammation of the brain.

"If [West Nile] goes that route, then it would be a situation where it's sort of oscillating," explained Dawn Wesson, an associate professor at the Tulane School of Public Health and Tropical Medicine in New Orleans. "Every few years we'd have an outbreak or some cases and then maybe not much activity between years."

The CDC's Roehrig agrees that this may be the path West Nile takes in the future, but cautions it will always be present.

"Every state every year will have some number of cases -- maybe it will just be a handful of cases, but it will never really just fade away completely like St. Louis encephalitis does," Roehrig said. "Even in the inter-epidemic period, there will always be some West Nile activity somewhere in the country."

Eyeing the next hotspot

Quickly spreading on its westward march across the nation, West Nile has infected mosquitoes, animals or humans in every state in the lower 48 in the past six years. (A North American fixture)

This season, California is the most likely hotspot if West Nile follows previous patterns, say authorities.

The state led the nation in number of cases last year at 771, and health officials say West Nile was just getting started.

More cases are expected as it becomes entrenched in the central and northern parts of the state and other parts of the West, according to Vicki Kramer, chief of vector-borne diseases at the California Department of Health.

"Because now it has been established and detected in all of California's counties by the end of 2004, we expect more widespread and earlier activity this year," Kramer said. "I'm sure we'll see more activity in Oregon and Washington as well."

Long-term effects?

For people like Leona Thrower, the long-term effects of West Nile are still unknown.

New studies suggest that even mild cases of West Nile -- often called West Nile fever -- may have lingering effects not known about a few years ago.

"It's being observed that even in cases of West Nile fever, which has always been characterized as a milder disease ... that it in and of itself in certain individuals can be a very severe disease and can take individuals quite a while to recover from it," said Roehrig.

Wesson explained that even though the illness has been present globally for decades, the volume of U.S. cases has allowed scientists to study the effects more closely among a wider range of individuals.

"[Scientists are looking at] potential long-term negative effects of having been infected, maybe not even being really sick -- maybe having a mild headache and other sorts of things -- but still having some minor neurological problems for extended periods of time," Wesson said. "As it's better studied, it seems there're more reports of that sort of thing out there."

Other mysteries for researchers involve birds. West Nile moves from one area into another depending on bird migration, or at least that's the theory. Wesson said that difficulty gathering data hinders a concrete solution. (West Nile and animals)

Also, birds in the Corvidae family, such as crows and blue jays, are more susceptible to West Nile than others, and researchers don't know why.

"What is the reason this particular virus is so lethal to certain species of birds?" Roehrig questioned. "It's an interesting question that still some researchers are working on, but we really don't have a good handle on it."

Precautions not panic

One area of progress for researchers is a West Nile vaccine for humans. In May 2005, the Cambridge, Massachusetts, biotech company Acambis reported promising results in the first stage of human trials. But federal health officials caution that vaccine availability for the public is still several years away.


Ridding your yard of standing water can lower the numbers of mosquitoes.

For now, experts urge the same tips to avoid West Nile carrying mosquitoes they've issued in the past, such as wearing long-sleeved shirts and pants outside and fixing window and door screens so mosquitoes don't enter the house.

This year, though, the CDC expanded its recommendations of bug repellent to include those with the chemical picaridin and oil of lemon eucalyptus in addition to those containing DEET. And they're also warning against complacency.

"There's always a tendency to get comfortable with the fact that this disease is out there, especially if you live in a place where you've had West Nile for four or five years and never been infected," .

"That's always a problem," he continued. "How do you keep people not panicked about this, but at least aware of the fact that if it's summertime, it's West Nile time and you have to think about taking some precautions."

After her experience with West Nile, Thrower always has bug repellent close at hand for a trip outdoors for her or her husband, and she is more aware of yard conditions that encourage mosquito breeding, such as standing water.

"When you go out, you see bugs flying around and you're immediately alerted to them," she said. "We are just very cautious now."