For information on insect repellents, go to the Centers for Disease Control website: http://www.cdc.gov/ncidod/dvbid/westnile/RepellentUpdates.htm.
To report swarms of mosquitoes, call the San Angelo health department at 325-657-4493.
SAN ANGELO, Texas — West Nile virus has killed one person and hospitalized three others in the most severe outbreak of the mosquito-borne disease ever seen in Tom Green County.
Dr. Irv Zeitler, vice president of medical affairs at Shannon Medical Center, said Tuesday the four cases have come into the center since July 27. He declined to specify the date of death for the fatality out of concern that it might identify the patient.
"It's very unusual for us to have this many neuroinvasive cases in such a short period of time," said Zeitler, a family practice doctor. "We thought it would be appropriate to get the information out to folks about prevention.
"The risk is not high, but it is present."
West Nile virus first appeared in Texas in 2002, and the first cases in Tom Green County were recorded the same year. The disease is transmitted by mosquitoes, and most people — 80 percent — who are infected show no symptoms. Another 20 percent get mild symptoms including fever and aches. But 1 percent of those infected get the neuroinvasive iteration of the disease, which can be fatal.
Working backward from the four neuroinvasive cases, the statistical probability suggests about 400 people in the county might be infected, of whom 80 might have the milder symptoms.
Zeitler said there appeared to be no geographic pattern in the four cases and they seemed to have nothing in common, such as being near water. "The real risk is being outside and being exposed to mosquitoes," he said.
There is no anti-virus or vaccine for West Nile, Zeitler said, and people who seek medical help are given symptomatic treatments such as hydration and pain control medication.
"Often with symptomatic treatment, there's a good outcome," he said. "What cures this disease is our own immune system."
He said the neuroinvasive form is seen almost exclusively in people older than 50 who often have other health problems and an increased risk of complications. Any conditions that affect the immune system — or conditions requiring immunosuppressive medication such as chemotherapy, organ transplants or even steroid medication for asthma — put people at greater risk of developing the more severe form of West Nile, he said.
"Symptoms mimic a stroke," Zeitler said. "People come in with very severe headaches, often confused. There could be vocal paralysis or visual changes, depending on what part of the brain is swelling."
The diagnosis is confirmed with a blood test and sometimes a lumbar puncture, he said.
Sherian Briley, marketing director for San Angelo Community Medical Center, said the hospital has not reported any West Nile cases this year.
Texas State Department of Health records show that one neuroinvasive case occurred in Tom Green County in 2002 and another in 2003, but neither was fatal.
The identity of the person who died this year from the disease is not a matter of public record, but Sandra Villareal, director of public health for the city of San Angelo, said the victim was a resident of Eden and the fatality would be reported for Concho County, not Tom Green County.
The outbreak this year is Texas-wide. Christine Mann, a spokeswoman for the Texas Department of State Health Services, said 16 deaths and more than 380 cases have been confirmed around the state, many of them in the Dallas-Fort Worth area, where nine deaths have been reported.
"Texas is on track to have the worst year ever for West Nile," she said. Reasons for the strength of the outbreak are not yet clear, she said, but contributing factors could include a warm winter followed by heavy spring rains, creating favorable conditions for mosquitoes.
The city of San Angelo uses chemical spray delivered by trucks to keep mosquito populations down, although with the drought they haven't been unusually busy, Rick Dickson, the city's director of operations, said Tuesday.
"Right now, we're just spraying hot spots like … Red Arroyo, places where mosquitoes breed," he said. The city will respond to individual householders' reports about swarms of mosquitoes, he said.
"We check on complaint areas," he said. "A lot of people have standing water on their property, and we get complaints after rains."
"People don't realize how little water it takes for mosquitoes to breed," he said. "We try educate homeowners."
Mann said this time of year is the peak of the West Nile season.
"We may be better able to analyze the causes for this once the season is complete," she said.
Repellents, coverings vital to protection
Follow these guidelines to protect yourself from mosquito bites:
Apply insect repellent to exposed skin. Generally, the more active ingredient a repellent contains, the longer it can protect you from mosquito bites. A higher percentage of active ingredient in a repellent does not mean your protection is better — just that it will last longer. Choose a repellent that provides protection for the amount of time you will be outdoors.
Repellents may irritate the eyes and mouth, so avoid applying repellent to the hands of children.
Whenever you use an insecticide or insect repellent, read and follow the manufacturer’s directions for use, as printed on the product.
Spray clothing with repellents containing permethrin or another EPA-registered repellent since mosquitoes may bite through thin clothing. Do not apply repellents containing permethrin directly to exposed skin. Do not apply repellent to skin under your clothing.
When weather permits, wear long-sleeved shirts and long pants when you are outdoors.
Place mosquito netting over infant carriers when you are outdoors with infants.
Consider staying indoors at dawn, dusk and in the early evening, which are peak mosquito-biting times.
Install or repair window and door screens so mosquitoes cannot get indoors.
Help reduce the number of mosquitoes in areas outdoors where you work or play by draining sources of standing water. Such actions reduce the number of places mosquitoes can lay their eggs and breed.
At least once or twice a week, empty water from flower pots, pet food and water dishes, birdbaths, swimming pool covers, buckets, barrels and cans.
Clean out clogged rain gutters.
Remove discarded tires and other items that could collect water.
Be sure to check for containers or trash in places that may be hard to see, such as under bushes or under your home.
Note: Vitamin B and “ultrasonic” devices are not effective in preventing mosquito bites.
Source: Centers for Disease Control and Prevention