Topeka's population of mosquitoes is 'severe,' forecast tool says, but county refutes number

Tim Hrenchir, Topeka Capital-Journal
·4 min read

Is Topeka abuzz with mosquitoes?

The answer is — depends on who you ask.

On the side of "yes" is a new forecasting tool created through a partnership between Google and Off!, the insect repellant.

That tool says city's predicted population of that blood-sucking insect Monday was at its highest possible level of "severe" and should remain so through Thursday.

Off!Cast predicts mosquito populations for up to seven days in advance, according to press materials from Off!

Topeka's Off!Cast Mosquito Forecast predicted the capital city for the second straight week last week would see a "very high" mosquito population, with "very high" being the second-highest of Off!Cast's five severity levels.

A Shawnee County Health Department employee checks a trap that department maintains to monitor the presence of mosquitoes.
A Shawnee County Health Department employee checks a trap that department maintains to monitor the presence of mosquitoes.

The forecast then worsened, with Topeka's predicted rating for Monday being identified as "severe" on the Off!Cast website. That site predicts Topeka's rating will remain at that level until it is lowered to "very high" Friday.

On the "no" side is testing by the Shawnee County Health Department, which says the mosquito population is lower than average this year.

"We did see a small increase last week in mosquitoes, but overall for the year, our mosquito population has been lower than the average," said Craig Barnes, division manager of community health outreach and planning for that department.

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Shawnee County Health Department tracks mosquito populations

Topeka's mosquito population is at its highest possible level, severe, says a forecasting tool created by Google and Off!, an insect repellant brand.
Topeka's mosquito population is at its highest possible level, severe, says a forecasting tool created by Google and Off!, an insect repellant brand.

The county health department since 2017 has teamed up with Sedgwick and Reno counties and the Kansas Department of Health and Education to conduct mosquito surveillance each year.

"We deploy five traps throughout Shawnee County on a weekly basis that track the overall number of mosquitoes and the potential presence of West Nile Virus, a mosquito-borne disease," Barnes said.

Those traps are located in various parts of the county. The samples are sent to the KDHE for analysis that includes testing for the presence of viruses.

No traps so far this year have identified the presence of West Nile Virus, Barnes said.

The county posts information online about its mosquito surveillance program, he said.

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How does the mosquito forecasting tool work?

The Off!Cast Mosquito Forecast is powered by Google Cloud’s geospatial and data analytics technologies.

It is the world’s first public technology platform that predicts and shares mosquito abundance information, according to a news release Google put out in May.

"By applying data that is informed by the science of mosquito biology, Off!Cast accurately predicts mosquito behavior and mosquito populations in specific geographical locations," the release said.

The Off!Cast model combines three inputs, according to its website.

Those are knowledge of a mosquito’s lifecycle, detailed climate data inputs and mosquito population counts from more than 5,000 locations provided by VectorBase, a resource center website of the U.S.  Department of Health and Human Services.

"To determine accuracy, our team spent six years checking the model’s results against live populations, generating 33 million data points," says the Off!Cast website. "The results confirm model predictions match the reality on the ground."

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What are Off!Cast's severity levels for mosquito population?

The Shawnee County Health Department says the local mosquito population is lower than average this year despite a new tracking tool that says the numbers are high.
The Shawnee County Health Department says the local mosquito population is lower than average this year despite a new tracking tool that says the numbers are high.

The Off!Cast website uses five severity levels, for which it provides these descriptions:

  • Low/Green, meaning people are safe to go outside and enjoy the outdoors.

  • Medium/Yellow, meaning people don't yet have to be super concerned, but the conditions are right for some mosquitoes to come out.

  • High/Orange, meaning mosquitoes are out and people will want to protect themselves.

  • Very High/Red, meaning prime conditions for mosquitoes have been in place for several days — likely resulting in increased mosquito activity.

  • And Severe/Dark Red, meaning conditions have been perfect for at least 14 days for mosquitoes to become active and breed, which means there are likely to be more of them.

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How does Off!Cast factor in humidity for mosquitoes?

This week's "severe" mosquito population forecast for Tuesday, Wednesday, and Thursday in Topeka comes at a time when Topekans have recently been coping with high temperatures and humidity.

Mercury readings and humidity are the primary factors used to create the mosquito forecast, though "it's a little more complicated than that," the Off!Cast website says.

"For example, there needs to be enough consecutive days of warmer temperatures for mosquitoes to populate and become active," it said. "There are also days that are 'too hot' when mosquitoes tend to lie low, and days that are 'too cold' when mosquitoes are less active."

Off!Cast automatically adjusts its algorithm for those days, its website said.

Tim Hrenchir can be reached at threnchir@gannett.com or 785-213-5934.

This article originally appeared on Topeka Capital-Journal: Mosquito population here has become 'severe," Topekans warned