Are mosquitoes worse in Wisconsin this year?

If you feel like mosquitoes are around more this year than the past couple summers, you're not imagining it.

After several years of drought, above-average rain this summer seems to have brought mosquitoes back out in full force. Here's the rundown on how much more mosquito activity we're seeing in Wisconsin this year, and how you can best protect yourself from bites and diseases.

Are there more mosquitoes in Wisconsin this year?

Last year, Wisconsin logged a historically dry spring, making it a low year for mosquitoes, which generally thrive in rain and humidity.

The dryness has abated this year, but even after a drought, mosquito egg banks are generally low and need some time to rebuild egg stocks, according to UW-Madison entomology professor Susan Paskewitz. Still, that doesn't seem to have stopped mosquitoes in Wisconsin from surging back, she said.

"In Wisconsin, we're hearing a lot of anecdotal reports, and experiencing some of it ourselves, that the numbers of mosquitoes are higher this year than they have been in the last couple years," Paskewitz said.

Paskewitz, who is based in Madison, said the last couple years she noticed barely any mosquitoes at the city's lakefront Fourth of July fireworks. This year, she said the mosquitoes were back out in full force bugging people throughout the evening.

Unlike other Midwestern states, including Minnesota and Illinois, Wisconsin does not have a tax-funded Mosquito Control District, which surveys and controls mosquito levels. This makes it harder to decisively compare mosquito numbers in Wisconsin this year compared to past years, Paskewitz said, but, so far, the mosquito levels across the state don't appear to be abnormally high.

Rather, the prevalence of mosquitoes is a return to normal levels after several years of below-average levels and abnormally low mosquito levels, she said.

Data from the Chicago's North Shore Mosquito Abatement District, which reports mosquitoes collected per night in traps across the city's northern suburbs, backs this up: in Northbrook, Illinois, a suburb about an hour from Milwaukee, mosquito levels this summer have been on par with the past ten years after historic lows last year.

Is there an increased risk of West Nile virus in Wisconsin this year?

Most mosquitoes people encounter are "nuisance mosquitoes" — mosquitoes that will bite and irritate, but will not spread harmful viruses like West Nile, dengue and Zika.

Wisconsin has not reported any human cases of West Nile virus this year, according to the Centers for Disease Control and Prevention, though the Wisconsin Department of Health Services did log 25 confirmed and probable cases in 2023. No Wisconsin counties are reporting animal, human or mosquito activity of the virus, as of June 6.

Above-average rain can also sometimes reduce the risk of West Nile virus, according to Paskewitz, because areas of standing water that may be housing diseased mosquitoes get flooded out. However, surveillance sites in Illinois and Minnesota reported early detections of West Nile this year in mosquitoes that inhabit underground water systems, she said.

Though West Nile isn't a source of concern in Wisconsin so far this year, the humid, drizzly summer may create a perfect storm for infection rates to rise across the country, she said.

"I do think [other states] are a little nervous," Paskewitz said. "They're doing a lot of control down there to try to damp things down."

How to protect yourself from mosquitoes

There are several simple, low-cost ways to protect yourself from mosquitoes if you're finding the insects are pestering you more than normal this year. Paskewitz offered the following tips:

• Avoid having standing water around your home. Buckets of water should be emptied out and bird bath water should be kept clean to avoid creating spaces for mosquitoes to lay eggs.
• Use insect repellent. Products with DEET, a key ingredient in many repellents, will be especially effective; but if you're looking for a plant-based option, repellents with lemon eucalyptus are also proven to work.
• Wear long sleeves and pants outside, especially during peak mosquito hours around sunset.
• If you're sitting outside, use an outdoor fan to disturb and deter mosquitoes' flight.