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Illnesses Spread by Mosquitoes in Wisconsin

There are many illnesses spread by mosquitoes in Wisconsin. Not all mosquitoes spread illnesses, and you won't get sick from every mosquito bite, but it is important to make sure you are aware of mosquitoes, the illnesses they can spread, and how to prevent bites in the first place.

Mosquitoes 101

  • Basics. Mosquitoes are a type of fly. In Wisconsin, there are many types of mosquitoes, but only some types can spread illnesses. Most people who get sick from a mosquito bite will become ill in the summer and early fall. This is when mosquitoes are most active and people are outdoors.
  • Life cycle. Mosquitoes have a life cycle that includes four different stages: egg, larva, pupa, and adult. Female mosquitoes lay their eggs on or near water, and the eggs hatch after coming into contact with the water. After hatching, the larvae will feed until they have enough energy to change into pupae. The pupae then grow into adult mosquitoes, the only flying stage. Only adult female mosquitoes bite humans and other animals to get blood meals, after which they lay their eggs on or near water, starting the cycle again. The life cycle of a mosquito usually takes two weeks. However, it can range from four days to one month.
  • Habitat. Mosquitoes live in areas with slow-moving or stagnant water, as well as forests, marshes, and tall grasses. Mosquitoes fly and land on animals or humans to bite the host's skin and consume blood. Warmer and wetter climates can increase the risk of getting an illness from a mosquito. In Wisconsin, climate change has created favorable conditions for mosquitoes to survive in more areas of the state, has made the mosquito season longer, and allows infected mosquitoes to spread diseases faster. For more information, visit our Climate and Infectious Disease page.

    In general, mosquitoes can be divided into two different types based on the habitats where they lay their eggs: standing water mosquitoes and floodwater mosquitoes. Most mosquito eggs need small amounts of water to hatch and develop into adult mosquitoes. For more information on the mosquito life cycle, and how to prevent mosquitoes around your home, visit the Environmental Protection Agency (EPA) website.

  • Prevention. The best way to avoid getting sick from a mosquito is to prevent bites in the first place. There are many ways to prevent mosquito bites, including wearing insect repellent and wearing appropriate clothes when you are outdoors. Check out other tips to prevent mosquito bites!

West Nile Virus

Mosquito biting a human

West Nile virus is spread by the bite of an infected mosquito. Find information about about this virus.

Jamestown Canyon Virus

Common mosquito on leaf

Jamestown Canyon is relatively rare in Wisconsin, but the number of reported cases has recently increased.

La Crosse Encephalitis Virus

Close-up of a mosquito on a black background

Mosquitoes that spread La Crosse encephalitis can be found throughout Wisconsin.

Eastern Equine Encephalitis Virus

Family trekking on a path in the forest

Eastern equine encephalitis is a rare but severe illness spread by the bite of an infected mosquito. People who spend more time outdoors are at a higher risk of being bitten by an infected mosquito.

St. Louis Encephalitis Virus

The mosquitoes that spread St. Louis encephalitis can be found in areas near standing water, which they need to breed. It is important to remove standing water sources to reduce breeding habitats in your yard.

Travel-Associated Illnesses

Silhouette of a jet against a cloudy sky

Travel-associated illnesses spread by mosquitoes are illnesses that people can get while traveling outside of Wisconsin and often outside of the U.S. It is important to take steps to protect yourself and your family while traveling


General public

Health care professionals

Vectorborne Disease Toolkit, P-01109 (PDF): A planning guide for public health and emergency planning professionals.

Resources can be ordered for free from DHS. Here's how

Questions about illnesses spread by mosquitoes? Contact us!
Phone: 608-267-9003 | Fax: 608-261-4976


Last revised July 9, 2024