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 » Symptoms  |  How it's spread  | Reducing risks  |  Special Report

U.S. braces for return of West Nile virus

By Amy Cox
CNN


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(CNN) -- Before there was SARS, there was West Nile virus. And with the arrival of summer, the re-emergence of mosquitoes and the resurgence of West Nile cases won't be far behind, say experts.

"I think the smart money would say we're going to have another heavy season of West Nile virus this summer because of the wet spring, (which means) a lot of mosquitoes," Dr. Daniel Blumenthal, an infectious disease expert from Morehouse School of Medicine in Atlanta, told CNN.

Dan O'Leary with the Centers for Disease Control and Prevention, said there is no way to predict exactly what will happen this year, but that there is evidence in some states -- such as Florida and Louisiana -- of early West Nile activity in mosquitoes, birds and animals.

Unlike severe acute respiratory syndrome, West Nile has proven deadly in the United States. In 2002, 284 people died from the disease, according to the CDC, which reported more than 4,000 cases nationwide last year.

By the end of 2002, all but four states -- Oregon, Nevada, Utah, Arizona -- in the continental United States had had either human cases or animal infections. But health officials expect to see reports of the disease in all of the lower 48 states this year.

"We expect, based on the spread since 1999, the continued expansion into Western states," O'Leary, based in Fort Collins, Colorado, said in a phone interview. "By year's end, those states [without cases last year] will have activity in either animals or humans."

Mosquito now a public enemy

The virus, first identified in 1937 in the West Nile region of Uganda, spread to the United States four years ago. It can cause encephalitis, a sometimes fatal inflammation of the brain.

There have been no confirmed human cases this season, but animal, bird and mosquito infections are already being reported in more than a dozen states, O'Leary said.

Illinois, for example, recorded its first infected bird of the year in May. Illinois, one of the hardest hit states in last year's outbreak, recorded 884 human cases and 64 deaths by the end of 2002.

Linn Haramis, an entomologist with the Illinois Department of Public Health, said the state is experiencing a slower start to cases than in the past because of the cooler spring. But he warns that all it takes is a couple of weeks of very warm weather for the mosquito -- and then West Nile activity -- to heat up.

Pants and long-sleeved shirts along with repellent help protect against mosquitoes.
Pants and long-sleeved shirts along with repellent help protect against mosquitoes.

"Weather has been with us but it can turn around very quickly," he said.

Haramis said that West Nile has the potential of being a routine problem. Unlike some other insect-borne viruses, West Nile does well in most U.S. climates, he said, and a variety of mosquito species are capable of carrying it.

Mosquitos become infected from biting infected birds, a natural host of the West Nile virus. In turn, the mosquitoes can infect humans, animals and even give it back to birds with their bites.

West Nile virus cannot be transmitted person-to-person through casual contact such as touching or kissing, according to the CDC.

The CDC reports that most infected people never show any signs of the illness, but about 20 percent may experience flu-like symptoms such as fever, headache and body aches. In a small number of cases, the virus causes sometimes fatal West Nile encephalitis or meningitis (inflammations of the brain or of the membranes around the spinal cord and brain).

Prevention is best medicine

But there's room for optimism in this fight. Blumenthal said researchers believe that once someone gets the virus, whether they show symptoms or not, they become permanently immune to West Nile virus.

Currently, there are no drugs or vaccine available to the public to treat the virus, although the government has screened more than 300 drugs for possibilities and research continues to develop a vaccine.

Prevention is key. Some practical tips to avoid mosquitoes from the CDC include:

• Wear long-sleeved shirts and pants when outside

• Stay indoors at dawn and dusk, when mosquitoes are most active

• Spray clothing and exposed skin with repellents containing DEET

• Get rid of standing water in yards and clean out clogged gutters, which are breeding grounds for mosquitoes.

Most of all, experts say not to panic about West Nile virus. Even if a person is bitten by mosquitoes, the risk of contracting the virus is low. According to government figures, only 1 percent of mosquitoes carry it in areas where the virus is established. And less than 1 percent of people bitten by those mosquitoes ever develop serious symptoms.

"There were 284 deaths from West Nile virus last year, (but) 30,000 deaths from pneumonia and influenza, and those are diseases that we can immunize against," Blumenthal advised. "So this is still a quite rare condition and not something that people should be overly concerned about."


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