Answers sought from West Nile surge
Health workers seek clues to 2012’s deadly outbreak in effort to prevent deaths.
With the mosquito population decimated by the cooler weather, experts have turned their attention to learning lessons from the latest round of deadly West Nile cases.
DALLAS — West Nile deaths mounted quickly this summer as mosquitoes spread the virus across the country. The situation was especially dire in Texas, where some areas resorted to aerial spraying for the first time in decades to curb what became one of the worst such outbreaks in U.S. history.
Nationally, more than 240 people died from the mosquito-borne illness — about a third of them in Texas, and at least six in Travis County.
Now with the mosquito population decimated by the colder weather, health experts have turned their attention to learning lessons from the latest round of deadly cases. Federal health authorities are collecting and examining data, while Dallas County — the epicenter of the outbreak — has begun year-round mosquito surveillance and testing.
What remains unclear is whether experts will be able to shed light on what caused the outbreak, why parts of Texas were so severely affected and whether they can forecast the next major surge in the illness.
“I don’t think that we’re ever going to totally be able to sort it out,” said Dr. Lyle Petersen of the U.S. Centers for Disease Control and Prevention. “For one reason, the ecology in the United States is extremely varied, so a factor that may affect an outbreak in Colorado may be different than a factor that causes an outbreak in Louisiana. The conditions in an urban area may be different than a sub-
West Nile virus is believed to have first appeared in the U.S. in 1999 in the New York City area and then gradually spread across the country.
Mosquitoes get the virus from feeding on infected birds, and then the insects spread it to people they bite. Most infected people show no symptoms, but the most severe form of the disease, called neuroinvasive, can cause coma, convulsions, muscle weakness, paralysis and death.
The Texas Department of State Health Services reported more than 835 neuroinvasive cases in Texas this year with 86 deaths, led by Dallas County’s 18 fatalities. The national death toll this year approached record numbers from 2002, when 284 people died from the disease.
Petersen said the CDC is trying to determine what caused the latest outbreak by looking at factors such as heat, rainfall and the number of migrating birds that transmit the virus to mosquitoes.
The agency is also researching the genetics of the virus to see if it might have mutated, but that doesn’t seem to have happened.
The situation became so severe in North Texas that the state paid for aerial spraying in areas of Dallas County and nearby Denton County. Dallas County hadn’t conducted such an operation since 1966 when encephalitis was blamed for more than a dozen deaths.
“If you look at this outbreak, it came upon us very suddenly,” Dallas County Judge Clay Jenkins said. “We might have the same situation in the future where, by the time people know there is a risk out there, dozens of people have already been infected.”
Dr. Don Read has made a mission of spreading the word about taking precautions. The 70-year-old Dallas colon and rectal surgeon contracted the neuroinvasive form in 2005 and still wears leg braces from the ordeal.
“I tell people it’s something you don’t want to have,” said Read, who formed a support group of survivors. “Initially, my legs were completely paralyzed. My arms were partly paralyzed. I couldn’t talk. I couldn’t hear. I couldn’t write.”
There’s no way to tell how bad West Nile will be or where it will strike, but Dallas County has added two microbiologists to handle yearround mosquito testing, said Zachary Thompson, director of Dallas County Health and Human Services. Jenkins added that they can now get test results in one day instead of seven.
Thompson said they will also start advising residents earlier in the year to apply insect repellent; dress in long sleeves and long pants when outside; stay indoors from dusk to dawn; and drain standing water on their property.
Jenkins noted: “Personal responsibility is important because we can’t possibly kill every West Nile mosquito.” discovery was initially investigated as a homicide, a police official said Tuesday. The official also had said the body appeared to have suffered “obvious trauma.” However, authorities said Wednesday that report was incorrect. An autopsy was performed and the death is no longer considered suspicious, officials said. An official cause of death has not been made, officials said, adding that a final ruling will be made following toxicology tests.