West Nile Infections High, But Peak Season Not Over Yet
A Texas health official says cases of West Nile virus this year could exceed 500, which would be a record for the state.
“From 2002-2011, the mean case count [in Texas] is approximately 225, ranging from 27 cases in 2011 to many more cases in 2003,” says Shelley Stonecipher, a zoonosis control veterinarian with the Texas Department of State Health Services in Region 2/3. “Most West Nile virus exposures are going to occur during the month of July through October, with the peak being during the first two weeks of August.”
Since 2002, health officials have been surveying mosquitoes by various methods, including mosquito pool surveillance, conducted by either city or county personnel, who will send the insects to the state laboratory in Austin for examination.
Stonecipher says approximately 80 percent of people infected with West Nile virus develop no clinical illness or symptoms at all.
“However, approximately 20 percent of the people who are infected who do develop symptoms; most of those people are going to develop what’s called West Nile fever. That typically manifests with flu-like symptoms such as fever, headache, rash or nausea and vomiting.”
She adds that roughly 1 out of every 150 people infected will develop the severe form of the virus, or West Nile neuroinvasive disease.
“High risk groups are going to be your elderly and immunocompromised and this form of the disease can result in meningitis and cephalitis. And of course it can be fatal as well.”
As of July 31, 47 cases of West Nile had been identified in humans in Tarrant County, the most of any Texas county. Another 37 cases are in Dallas and seven in Collin County. A seventh person died in Texas from the virus Friday.
The most common defense continues to be consistent use of mosquito repellant when outdoors and removal of any standing water on your property. A number of cities also spray for mosquitoes during the summer.
“Certainly mosquito control is always recommended to the ability that any community can do so. Anything that reduces the number of mosquitoes is usually going to help,” said Stonecipher.