The big picture
A typical “mosquito season” runs May-November because those are the months that consistently see mosquito-friendly temperatures of above 50 degrees Fahrenheit, said Richard Milam, health compliance manager for the city of McKinney.
“[The end of mosquito season] is not a day on the calendar you can look for,” Milam said. “It’s more about the temperatures. What we’re looking for to knock down the mosquito population is temperatures to be consistently in the mid- to lower-fifties overnight, that really drops the mosquito population down.”
As of Nov. 1, McKinney officials have reported more than 30 pools including West Nile virus-positive mosquitoes, including multiple repeat locations. A public map of the positives and spray areas can be found here.
A mosquito pool is a group of around 50 trapped mosquitoes collected from across the city. The mosquitoes are then sorted by species and sent off for testing at county and state health service departments, which then report their findings back to the city that supplied the mosquitoes.
West Nile virus is more common in warmer months but has the potential to be a year-round risk, according to a statement on the Texas Department of State Health Services’ website. For areas that experience warmer weather in the fall and winter months, something many Texans are especially familiar with, the breeding season for mosquitoes can become longer.
Milam said he has trapped virus-positive mosquitoes as late as the week of Thanksgiving. The lab that McKinney sends its mosquito samples to closes Dec. 1, roughly one month after the season ends, and reopens again in the spring.
Diving deeper
Mosquito surveillance reporting is voluntary but human cases of West Nile virus must be reported by law, said Grace Powers, an epidemiologist with Collin County Health Care Services, in an email.
A human West Nile virus positive could come from someone experiencing symptoms and goes to a doctor for testing, or from someone experiencing no symptoms but is tested anyway. The latter scenario occasionally happens to potential blood donors who attempt to donate but are later notified they tested positive for the virus during the screening process.
Blood donation positives from asymptomatic donors are referred to as viremic blood donor positives. They do not count toward the total number of positives unless they meet other reporting criteria, according to the Texas Department of State Health Services’ website.
It is not possible to contract West Nile virus by giving blood and the Centers for Disease Control and Prevention has stated contracting it through a transfusion is unlikely, said James Black, senior public relations specialist at Carter Blood Care, in an email. Regardless, blood collection agencies have screened donated blood for the virus since 2003 and virus-positive blood is incinerated, he said.
A positive mosquito pool or a confirmed human positive can set off spraying, Milam said. Spraying involves trucks, sometimes referred to as fogging trucks, spraying an insecticide mist in a one-mile radius of a positive to kill nearby mosquitoes that could carry the virus.
McKinney residents may have seen signs alerting them to scheduled mosquito spraying in their area over the past few months. The process is typically done overnight and is considered harmless to humans and pets when done correctly, but McKinney’s mosquito control website recommends residents and their pets stay inside to be safe.
Before you go
Here are the Texas Department of State Health Services’ recommendations for mosquito precaution and prevention:
- Wear long sleeves and pants outside at dawn and dusk when mosquitoes are most active.
- Use insect repellants if outside. Approved repellents contain DEET, picaridin or oil of lemon eucalyptus.
- Drain any standing water from bird baths, French drains, clogged gutters, saucers under potted plants and splash blocks. The mosquitoes that carry the virus can breed in as little as 1-2 teaspoons of standing water, according to the Denton County Public Health website.
