While concerns about the Zika virus have been in the headlines of late, Texas health officials reported the state’s first West Nile case of the year late last week, signaling the fact that disease-causing mosquitoes are out there — and a bit earlier than usual.
“A couple of factors put us at higher risk,” said Dr. Jason Bowling, staff epidemiologist at University Health System and an infectious disease specialist with UT Medicine. “One is the milder winter. A typical winter kills off most of the existing mosquito population from the prior year, but when it’s milder some of them can survive. And then with all this rain and flooding we’ve had, we have a lot more breeding ground for mosquitoes.”
Patients with West Nile infection typically have few or no symptoms, making diagnosis a challenge, Dr. Bowling said.
“The majority of people don’t have any symptoms with West Nile. About 80 percent of people are thought to be asymptomatic. Most people who do have symptoms have pretty mild symptoms. Only a very small number get the neuroinvasive disease, which is what you really worry about.”
Those at higher risk for neuroinvasive disease, which includes encephalitis or meningitis, are the elderly and those with weakened immune system from disease or treatment for cancer or transplants.
Dr. Bowling recommends that people consider taking precautions against mosquito bites. That includes the use of EPA-approved insect repellants, regularly draining standing water on your property and wearing long sleeves and pants outside. The San Antonio Metropolitan Health District has created a helpful new video to help people find and eliminate standing water around their homes. And with all the recent rains — and more in the forecast — there’s a good chance that most of us have some breeding grounds close to home.
Last year, Bexar County reported one case of neuroinvasive West Nile disease. Since 2012, a total of 23 neuroinvasive cases have been reported, in addition to a number of additional, milder West Nile fever cases.
Bexar County has seen six Zika infections in recent months — all of them local residents who had traveled to places where the virus is circulating. No locally transmitted cases have been reported yet.
West Nile virus is primarily spread by Culex mosquitoes, which like to bite people around dawn and dusk, while Zika is transmitted largely by Aedes mosquitoes, which prefer the day.
“We have both,” Dr. Bowling said, adding that the same precautions protect against both types of mosquito.
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