What Cities Are Seeing the Biggest Mosquito Swarms?

As several state health departments report mosquito populations with West Nile virus, some U.S. cities are feeling more mosquito hotspots than others.

According to Orkin’s 2025 Top 50 Mosquito Cities List, Los Angeles claims the No. 1 spot for the fourth year in a row. Chicago, New York, Atlanta, and Detroit round out this year’s top five, with Detroit making its first appearance in the top rankings. Houston, Dallas, and Washington, D.C., ranked six through eight, respectively. Cleveland and Denver also broke into the top 10 for the first time at the No. 9 and 10 spots, signaling larger mosquito pressure in northern cities as temperatures climb.

The annual list is based on the number of new residential mosquito treatments performed by Orkin from April 1, 2024, through March 31.

California remains a stronghold for mosquito activity overall, with five cities in the Top 50: Los Angeles, San Francisco, Sacramento, San Diego, and Fresno. With high temperatures and proximity to standing water, mosquitoes are frequent residents of the West Coast state.

Mosquitoes are responsible for more deaths annually than any other creature, causing over 600,000 malaria-related deaths each year, according to the U.S. Centers for Disease Control and Prevention. Last year, for the first time in 20 years, the United States experienced cases of locally acquired mosquito-transmitted malaria. Mosquitoes also transmit other dangerous diseases such as West Nile virus, eastern equine encephalitis, dengue, chikungunya, and zika virus.