West Nile virus: Texas calls in CDC to help control outbreak

HOUSTON -- Texas public health officials called in experts from the Centers for Disease Control and Prevention this week to help control the worst outbreak of West Nile virus in the country.

Dallas County is the epicenter of the outbreak, with 262 West Nile infections reported (20 last weekend) and 10 deaths. Texas has seen 586 West Nile infections reported this year and 21 deaths, according to state figures.

So far this year, the CDC has reported 693 West Nile infections nationwide and 26 deaths.

Dallas-area officials declared a public health emergency this month and launched the first aerial pesticide spraying effort in more than 45 years. On Monday, five planes completed the first four-day round of spraying to combat the spread of the mosquito-borne virus, a controversial undertaking that drew protest from some worried about the pyrethrin-based pesticide, Duet, despite reassurances that it is approved by the CDC and EPA.

Laura McGowan, a spokeswoman for the mosquito control company spraying the area, told the Los Angeles Times that workers covered 362,000 acres and planned to trap mosquitoes late Tuesday to gauge the effectiveness of their efforts. Earlier trapping showed signs of success, she said, but was not statistically significant.

Spraying started Thursday night and was halted Saturday due to storms. It resumed Sunday.

Dallas County cities had until 2 p.m. Tuesday to opt into another round of spraying. It was not clear how soon that would start, though it is likely this week, McGowan said.

“The goal is to get as much of it done in as short a time as possible,” she said.

McGowan cautioned that pesticide spraying should not give Dallas-area residents a false sense of security.

“We want to protect against that reaction that, ‘Oh, they sprayed so I can go out without my DEET.’ People need to be vigilant about standing water, especially after all the rain we’ve had this week,” McGowan said.

Her company, Roselle, Ill.-based Clarke, plans to work with CDC experts sent in to help control the outbreak, she said.

At the request of Texas public health officials, the CDC sent two epidemiologists to the Dallas area this week as an “Epi-Aid response,” according to CDC spokeswoman Kristen Nordlund.

The epidemiologists, who will be based in Arlington, plan to “help to summarize statewide data for West Nile virus activity in mosquitoes and humans and help evaluate conditions that may be associated with the higher numbers of human infections in 2012,” Nordlund told The Times.

The West Nile virus incubation period can last up to two weeks, so state officials do not expect weekend spraying to halt the rising number of cases in the Dallas area immediately.

“We expect to see more cases — that’s the nature of the way the illness works with a 14-day incubation period,” Carrie Williams, a spokeswoman for the Texas Department of State Health Services, told The Times. “The numbers will go higher before we start to see positive results from our efforts.”

She said there have been no other large outbreaks in other parts of the state or requests for aerial spraying. Although West Nile season usually peaks in Texas in August, Williams said the number of infections was still increasing and it was too soon to tell when it might start to dip.

“We won’t know until we have a complete picture of how the season unfolded,” she said.

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