Chicago's mosquito days are swelling
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A Culex pipien mosquito specimen in the insect collection at the Field Museum shows the type of mosquito that carries the West Nile virus. Photo: E. Jason Wambsgans/Chicago Tribune/Tribune News Service via Getty Images
It's mosquito season, and Chicago is buzzing.
Driving the news: The number of "mosquito days" — those with hot and humid weather the insects crave — has trended upward in Chicago over the past several decades, per a new analysis.
- The report, from nonprofit climate news organization Climate Central, defines a "mosquito day" as one with average relative humidity of 42% or higher, plus daily high temperatures of 50-95° F.
Why it matters: Mosquitoes carry diseases such as malaria, West Nile virus and Zika, Illinois health officials warn in this week's "Fight the Bite" campaign.
- Four counties in Illinois, including Cook, have detected West Nile in mosquitoes this year, but there have been no positive human cases, according to the Illinois Department of Public Health.
Flashback: IDPH reported eight deaths attributed to West Nile virus in 2022, the most since 2018.
By the numbers: Chicago had 142 mosquito days in 2022, compared with 128 in 1979 — a 14 day increase.
The big picture: Seventy-one percent of the 173 nationwide locations Climate Central analyzed saw an increase in mosquito days from 1979 to 2022 — about 16 days on average.
Of note: Other factors, such as rainfall and drought, can also influence mosquito activity.
- They breed in pools of standing water, common after major storms.
The bottom line: Mosquitos — and the diseases they sometimes carry — are shaping up as one more climate change-induced problem for many city officials to worry about.
- IDPH encourages "the three Rs" in fighting mosquito-borne diseases — reduce, repel and report.
Go deeper: Think you're sweet? Mosquitoes don't.