West Nile Virus

The government is trying to talk health workers into smallpox vaccinations and is battling a mysterious new ailment called SARS, but last year's health threat - the West Nile virus - is already making its way up the Mississippi River with the rising temperatures.

Although no new cases have been found in humans this year, six dead birds in Louisiana and two in Hinds County, Miss., have tested positive for the virus, which last year infected 4,161 Americans and killed 277, including 21 in the Mid-South, four of them in Shelby County.

Public health officials say there's a possibility fewer Americans could be infected this year.  But they're preparing for the worst.  The Memphis and Shelby County Health Department will start collecting and testing dead birds May 1.

Dr. Lyle Petersen, deputy director for medical science at the Centers for Disease Control and Prevention's division of vector-borne infectious diseases, said CDC personnel and funds are not being diverted from West Nile to other problems despite the attention to SARS and smallpox.

"Nobody knows whether more or fewer cases will occur this year compared to last year," he said.  "What is for certain is that the virus will continue its march westward and we expect more cases to occur in the Western states.  I wouldn't be surprised if every one of the continental United States had West Nile virus activity." 

The first clues to the threat of West Nile this year could come in the South. "The best indicator of future epidemics will be the presence of human cases early in the season.  If we start seeing cases in early June then we know we've got a big problem," said Petersen.

Some mosquito-borne illnesses go through a boom-and-bust cycle as the virus works its way through species of birds.  St. Louis Encephalitis, a relative of West Nile, struck more than 2,500 people in the Midwest from 1974 through 1977, but now usually only occurs in local outbreaks that average about 30 cases.

New York had a bad year for West Nile in 2001, but last year it was very light, noted Dr. Timothy Jones, Tennessee 's deputy state epidemiologist.  West Nile acted the same way in Russia , he added.

In humans, the virus can produce West Nile fever, with symptoms that include fever, headache, body aches, skin rash and swollen lymph glands, or the more serious West Nile encephalitis, with symptoms that may include high fever, headache, neck stiffness, disorientation, tremors, occasional convulsions, paralysis and coma.

People over 50 or with compromised immune systems are most at risk.  There is no cure and treatment is limited to easing symptoms to help the patient survive while the body fights off the virus.

A vaccine is available for horses, but not humans.  Acambis, a bio-tech company based in Cambridge , England , and Cambridge , Mass. , is developing a vaccine that is expected to go into clinical trials with human subjects in the next few months.  But data won't be available until the end of the year; government approval could be years away.

So the only way to control the disease is to control mosquitoes.  And the battle will be fought in the back yards, not the creeks and swamps.

There are lots of different kinds of mosquitoes, 55 species in Mississippi alone, including a particularly obnoxious variety that likes rice fields, said Sally Slavinski, an epidemiologist with the Mississippi Department of Health.

But it's the common house mosquito, Culex pipiens , which seldom strays more than a mile from its birthplace, is the main culprit in transmitting West Nile virus, Slavinski said.

The majority of Tennessee cases were in Memphis and even within the city there were "hot zones," said Jones, Tennessee 's deputy epidemiologist.

TIPS FOR PROTECTING AGAINST THE WEST NILE VIRUS

Here's what public health officials say you can do to protect yourself, your family and your neighbors against the mosquitoes carrying West Nile virus.

At home:  

• Throw away tin cans, plastic and ceramic pots or other water holding containers on your property, especially used tires.

• Drill holes in the bottom of recycling containers left outside.

• Clean gutters.

• Turn over wading pools and clean and chlorinate swimming pools when not in use.

• Stack wheelbarrows, buckets, barrels, boats and canoes upside down.

• Aerate fishponds and do not let water stagnate in birdbaths or pet bowls.

• Repair window screens.

• Don't rely on bug zappers or ultrasonic devices to eliminate all mosquitoes.

• Remember: Mosquitoes will develop in any puddle that lasts more than four days.

When you're out:  

• Wear long-sleeve shirts and long pants outdoors.  Light-colored clothes are less attractive to mosquitoes.

• Adults should use insect repellent containing 10 percent to 35 percent DEET (N ,N -diethyl-meta-toluamide).  Apply sparingly to exposed skin and clothing, but not on the face, cuts, bruises or skin damaged by sunburn and other skin conditions.  DEET is safe for pregnant and breast-feeding women.

• Do not use repellent on children under 3 and for older children only use products with up to 10 percent DEET.  Do not let children apply repellant themselves.

• Avoid the outdoors as much as possible during the early morning and early evening.  Don't picnic in mosquito-laden areas.

• Collect dead blue jays and crows, but only if they appear to have died recently.  Use plastic gloves or plastic bags to pick up the birds.  Store them in a plastic bag in a cooler or freezer and call your local public health department.

• In Shelby County , call the West Nile Virus hotline at (901) 544-7503.

• More information online:

www.cdc.gov/ncidod/dvbid/westnile

www.state.tn.us/health

www.msdh.state.ms.us

www.HealthyArkansas.com

http://westnilemaps.usgs.gov