Waiting for West Nile: Rain, heat create a ‘perfect storm’ for the virus in Idaho

Fight mosquitoes with these simple tips

Fight mosquitoes inside and outside with a few simple tips. Remember to cover windows with screens, remove standing water, and cover your skin with long sleeves and pants. And don't forget insect repellent.
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Fight mosquitoes inside and outside with a few simple tips. Remember to cover windows with screens, remove standing water, and cover your skin with long sleeves and pants. And don't forget insect repellent.

Debbie Harris felt sick for the better part of nine months after the mosquito bit her.

Harris was helping her daughter, Nikki, move into her Treasure Valley home in 2015. She thought nothing of the bite until a few weeks later when she began to feel strange.

Her symptoms ranged from headaches to body aches to feeling the sensation that she was slipping when she wasn’t. Every common winter cold felt like the flu; every morning was a struggle to get out of bed.

West Nile virus was the culprit. The ultimate irony was that Harris’ daughter had just taken a position as Payette County’s Mosquito Abatement District co-manager.

Debbie Harris said she still has symptoms that worry her to this day.

“It never goes away,” she said. “It’s scary because you don’t know how it’s going to affect you.”

This year was expected to be a bad West Nile season due to a combination of record rain, snow and heat. The virus doesn’t cause symptoms in most people, but those who do become sick may contract a fever or experience a more severe infection of their brain or spinal cord. People over age 50, with weakened immune systems or with other medical conditions are at greater risk for the neuroinvasive illness.

High temperatures and above-average rainfall are indicators that the virus may spread more widely, according to the National Center for Atmospheric Research. This year’s record downpours combined with unrelenting heat were a potential recipe for disaster.

That has not, so far, been the case. But West Nile infections tend to peak later in the summer, the data shows.

So far in 2017, five Idaho counties have had mosquitoes test positive for West Nile. Included are Ada, Bannock, Canyon, Gem and Payette. No people have yet reported contracting the virus.

In 2016, health officials tallied nine people and 10 horses with symptoms of West Nile infection, according to data from the Idaho Department of Health and Welfare. Ten counties across the state had mosquitoes test positive for the virus. Only one of those nine people had come down with symptoms by late July.

Most cases are discovered at the end of summer, said Sam Holt of Ada County’s Weed, Pest and Mosquito Abatement.

Holt said his team began planning this year’s West Nile precautions in the winter. “(Snow) is our indication for our next season,” he said.

Ada County captured 8,500 potential West Nile-transmitting mosquitoes in traps in a single week this June, according to data provided by the county. The same week in 2016 yielded fewer than 1,000.

“This is a very weird year,” said Holt, who serves as a program and education specialist.

And authorities remain on their toes.

“We have the perfect storm this year,” said Ed Burnett, Canyon County director of mosquito abatement. “The flood’s over, but boy I’m telling you, the mosquitoes are out there.”

Fight mosquitoes inside and outside with a few simple tips. Remember to cover windows with screens, remove standing water, and cover your skin with long sleeves and pants. And don't forget insect repellent.

Biology and a bad year

Idaho has many types of mosquitoes. Most are harmless, albeit annoying.

One genus, Culex mosquitoes, are the chief ones spreading West Nile in Idaho. They lay their eggs on the surface of water. Even a puddle can host eggs.

And this year, there have been many puddles. From December through April, Boise accumulated a total 11.04 inches of precipitation. The normal amount over that period of time is 6.4 inches, according to the National Weather Service.

The number of potential West Nile-transmitting mosquitoes caught in Ada County in that single week in June represented nine times the normal number of Culex mosquitoes. But the increase isn’t as significant in other counties. Payette, for example, had captured a total of 3,227 Culex mosquitoes when the Statesman talked to Nikki Harris last week — 12 more than at the same time last year, the Payette district co-manager said.

The reason: this spring’s Boise River flooding, including around Eagle Island, Holt said. The rain, snow and flooding created ideal breeding conditions in Ada County.

“It was the flooding. It made everything horrible,” Holt said. “I was able to get 360 mosquitoes out of a cow footprint.”

Then came hot weather. While water is the breeding ground, heat allows mosquito larvae to potentially hatch faster, according to the National Center for Atmospheric Research.

A mosquito typically takes five to 10 days to hatch and develop. Harris said Southwest Idaho’s current weather conditions have cut that time to about three days.

From July 1-16, Boise’s average daily high was 98.4 degrees — the third-highest average for that time on record, the NWS said last week. Since June 1, this summer is the seventh warmest on record.

This year’s heat is reminiscent of 2013, when West Nile was found at a slightly higher clip.

That year, seven people in Ada County were found to have West Nile fevers or the virus’s more worrying neuroinvasive symptoms. Next door, Canyon County authorities counted 14 such cases. State officials had heard of two infections in humans by late July, both in Payette County, said Niki Forbing-Orr, public information manager for Idaho Health and Welfare.

Much like this year, 2013 featured high temperatures, with the summer daily-high average for June, July and August reading 84.5, 97.5 and 93.7 degrees, respectively. July 2013 was nearly 7 degrees higher than normal.

Protect yourself

Because Ada County began preparing months before West Nile season began, Holt said it has been well-equipped for potential trouble. Holt estimates his team set up 150 traps this year. There are two main reasons he believes things are under control: efforts to exterminate mosquitoes before they hatch, and more importantly, public education.

“We’d much rather deal with a preventative measure than taking no action,” Holt said.

The simplest way not to contract West Nile is straightforward: Protect your skin. Put on bug spray and wear long sleeves and pants. A combination of that and abatement efforts from counties across the state has probably helped keep the virus in check, Forbing-Orr said.

She said people can also do themselves a favor by getting rid of any standing water on their property. That includes puddles, bird baths and spaces between your front lawn and sidewalk.

Perhaps less obvious is limiting your overall water use. Despite high temperatures, Canyon County’s Burnett said there is no reason to overwater your lawn. That just leads to the potential for more mosquito breeding grounds.

“When it gets hot, people tend to overwater. I think that’s one of the things, overwatering,” Burnett said. “Because that creates a whole problem for us.”

It’s only midsummer, and Holt and Forbing-Orr are still holding their collective breath.

“It has not passed,” Holt said. “This is the pivotal part. We’re still doing the grind.”

Michael Katz: 208-377-6444, @MichaelLKatz