Mosquitoes are a common presence in Chicago, as in many urban environments. They thrive in urban conditions, making their presence a regular occurrence throughout much of the year. Understanding their activity, potential health implications, and effective prevention strategies is important for residents and visitors.
Mosquito Activity in Chicago
Mosquito season in Illinois spans early April through mid-October, beginning when average overnight temperatures reach at least 50°F. This extended period allows for multiple generations of mosquitoes to develop. Several types of mosquitoes are found in the Chicago area, with the Culex pipiens, often called the Northern House Mosquito, being particularly common. The Culex mosquito is known to prefer biting birds, but it can also transmit viruses to humans. Other species present include the Aedes albopictus (Asian Tiger Mosquito), an aggressive day-biter, and the Aedes vexans (inland floodwater mosquito).
Mosquitoes lay eggs in standing water, abundant in urban settings due to artificial sources and drainage systems. Common breeding sites include:
Puddles
Storm drains
Clogged gutters
Discarded tires
Flowerpots
Neglected birdbaths or garbage cans
Health Risks from Mosquitoes
The main public health concern from mosquitoes in Chicago is West Nile Virus (WNV). This virus is the most common mosquito-borne disease in the United States. WNV transmission typically involves Culex mosquitoes becoming infected after feeding on virus-carrying birds, then transmitting it to humans through subsequent bites.
About 80% of individuals infected with WNV do not develop symptoms; however, about one in five may experience a mild illness. This milder form can include symptoms such as fever, headache, body aches, joint pains, vomiting, diarrhea, or a rash. A more serious illness, affecting the central nervous system, occurs in about one in 150 infected people. Severe symptoms can include high fever, severe headache, neck stiffness, confusion, tremors, paralysis, or vision loss. Individuals over 60 or those with compromised immune systems face a higher risk of severe complications. WNV activity, including positive mosquito pools and human cases, is regularly monitored in Cook County.
Protecting Yourself and Your Property
Proactive steps can significantly reduce exposure to mosquitoes and their breeding grounds. Personal protection measures include using EPA-registered insect repellents containing active ingredients such as DEET, picaridin, IR3535, or oil of lemon eucalyptus (OLE)/para-menthane-diol (PMD). Applying these repellents to exposed skin and clothing according to label instructions provides effective protection.
Wearing long-sleeved shirts, long pants, and socks, especially during peak mosquito activity at dawn and dusk, can help. Light-colored clothing is often recommended, as mosquitoes may be attracted to darker colors. Treating clothing and gear with permethrin, an insecticide that repels and kills mosquitoes, offers further protection. Permethrin should not be applied directly to skin.
Eliminating standing water on your property is a key step in mosquito control, as mosquitoes require water to lay eggs. Regularly emptying and scrubbing containers like flowerpots, birdbaths, pet dishes, buckets, and checking gutters for debris can prevent breeding. Ensuring windows and doors have intact screens prevents mosquitoes from entering your home. The Chicago Department of Public Health implements community-wide efforts, such as treating catch basins with larvicide and targeted spraying, to manage mosquito populations.