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As COVID-19 Declines, West Nile Virus Season Returns To North Texas

A Culex mosquito on a human hand.
West Nile virus is spread by the Culex species of mosquito.

Tarrant County Public Health recently confirmed its first positive sample of the disease in mosquito traps in Crowley. No human cases spotted, so far.

As the department's Vector Control Supervisor, Nina Dacko oversees surveillance for West Nile Virus in Tarrant County. She talked with KERA’s Sam Baker about the sighting.


Why Crowley?

Typically, our hotspot areas for West Nile Virus include the northeast portion, which has more population than the rest of the quadrants that divide Tarrant County. This time it's in the southwest.

Why Does Northeast Tarrant County Have More Positive Sightings?

When you look at areas where there are places with trees and rivers, where they're surrounded by suburban-type neighborhoods, where people could be supplying an area where mosquitoes could live — most of that's going to be more prominent in the Northeast. There's a lot of people with irrigation up in that area. And so more mosquitoes, more birds, more people. So where you have more of all of those things coming together, you're going to have more of a probability for West Nile Virus.

How Long After Finding A Virus Does Spraying Take Place?

It's all about looking at the risk. We have to look at the time of year. Are there other positives that have popped up in an area that's nearby? Is it a year that's been proceeded by little to no activity? We also have certain calculations. We'll do things like look at the infection rate of the mosquitoes.

When The Public Should Begin Taking Precautions

As long as there's mosquitoes out and about, folks should really take precautions on making sure they're protecting themselves after a rain event.

  • Make sure you're dumping your containers.
  • If you can't dump something, treat it with larvicides or things that you can put in the water to prevent larvae — things like mosquito dunks or mosquito bits available at a lot of local hardware stores.
  • Use repellents containing DEET.
  • Making sure there are no holes in the screens of your doors and windows that allow mosquitoes in your house.

How To Keep Mosquitoes Away From Your House.

Mostly, it's going to be trying to eliminate the sources where those mosquitoes are coming from. A lot of these areas you can't always find. You don't need a lot of water to breed a mosquito. A capful of water can work. French drains have a little grate that can hold a little bit of water. Even trees can have rock holes where mosquitoes can breed.

The Previous West Nile Season

Last year was actually a bad year for West Nile virus. It’s a bird-mosquito-bird transmission cycle, and just like people, birds can build immunity to the virus.

So if we have a period of time, say like two to three years, where we're not seeing a lot of activity, those birds that are immune to West Nile Virus are going to die off. And they're going to be replaced by susceptible hatchling birds that can replicate the virus and spread it throughout the bird population.

For a few years prior to last year, we didn't see a lot of activity. But last year, there was a lot of activity. This year. I would say, it's not very likely because we had a heavy year last year. And so the hope is a lot of the birds actually built up immunity.

There's a lot of things that come into play with that because there could be something that we miss with bird migration, or if there's a bird die-off of some sort, all of those things and the weather and the mosquito populations, all of those things kind of have to match up to have a big year.


Tarrant County Confirms First Positive West Nile Virus Sample of 2021 Season

West Nile Virus In Texas

CDC: West Nile Virus

Interview highlights were lightly edited for clarity.

Got a tip? Email Sam Baker at You can follow Sam on Twitter @srbkera.

KERA News is made possible through the generosity of our members. If you find this reporting valuable, consider making a tax-deductible gifttoday. Thank you.

Sam Baker is KERA's senior editor and local host for Morning Edition. The native of Beaumont, Texas, also edits and produces radio commentaries and Vital Signs, a series that's part of the station's Breakthroughs initiative. He also was the longtime host of KERA 13’s Emmy Award-winning public affairs program On the Record. He also won an Emmy in 2008 for KERA’s Sharing the Power: A Voter’s Voice Special, and has earned honors from the Associated Press and the Public Radio News Directors Inc.