California’s Mosquito Season Is Getting Longer, Experts Warn
Mosquito Awareness Week (April 19–25) is an important reminder that residents need to take action to prevent mosquito-borne diseases

 

SACRAMENTO, APRIL 15, 2026 – Mosquito season may be starting earlier and lasting longer across California, raising new public health concerns for mosquito-borne diseases like West Nile virus. As part of Mosquito Awareness Week (April 19–25), mosquito control districts across the state are warning residents that warmer temperatures and changing weather patterns are helping mosquitoes thrive for more months of the year.

 

In addition to West Nile virus, which is always present in our state, cases of locally transmitted dengue were reported again in 2025. The state also experienced two natural disasters in 2025, the Eaton and Palisades fires, which resulted in thousands of unmaintained swimming pools that served as potential breeding grounds for mosquitoes that are capable of transmitting disease.

 

“Mosquito and vector control districts throughout California continue to contend with growing mosquito-related threats that impact residents every year,” said Dr. Paula Macedo, president of the Mosquito and Vector Control Association of California and District Manager of the Contra Costa Mosquito and Vector Control District. “Unfortunately, these threats are growing due to warmer and longer summers as well as increasing natural disasters like wildfires and floods, which create new public health emergencies. Mosquito districts work to prevent mosquitoes from harming California residents and visitors, but they can’t do it alone. Residents need to take action and protect themselves from mosquitoes by dumping and draining standing water in and around their homes and wearing EPA-registered repellent.”

 

West Nile virus, spread by Culex mosquitoes, is the most prevalent and serious disease transmitted by mosquitoes in California. There is no human vaccine for West Nile virus, which can cause debilitating cases of meningitis, encephalitis, and even death. In 2025, there were 113 cases of West Nile virus, 11 of which were fatal. There have been more than 8,000 human cases and over 400 deaths reported in California since West Nile virus first appeared in California in 2003.

 

“Mosquito Awareness Week serves as an important reminder for all Californians that mosquitoes are more than just a nuisance; they're a real public health concern," said Assemblymember Greg Wallis. "ACR 170 recognizes the incredible work California's Mosquito & Vector Control Districts do day in and day out to keep communities safe from dangerous mosquito-borne diseases. It also reminds us that we all have a role in this fight. Simple steps like using repellent and dumping out standing water go a long way in keeping our neighborhoods safe”.

 

Everyone can do their part to help prevent mosquito bites:

• Eliminate all sources of standing water on your property, including in flowerpots, old tires, buckets, pet dishes, and trash cans. Mosquitoes can lay their eggs in as little as a bottle cap of water.
  
• Apply mosquito repellent containing an EPA-registered active ingredient, like DEET, picaridin, oil of lemon eucalyptus, or IR3535, to clothes and exposed skin according to label instructions. Repellents keep mosquitoes from biting. It is important to follow product label instructions for the safe use of repellents on children.
• Apply repellent after sunscreen application. 
• Install screens on windows and doors, and keep them in good working condition to keep mosquitoes out of your home.
• Repair leaking faucets and broken sprinklers that can contribute to standing water around your home.
• Clean rain gutters clogged with leaves.
• Dress in long sleeves and pants, especially if outside at dawn and dusk when mosquitoes that can spread West Nile virus are most active.
• Report neglected swimming pools and day-biting mosquitoes to your local mosquito and vector control agency (agency information can be found at mvcac.org)

To learn more, please visit the MVCAC website or the California Department of Public Health Mosquitoes and Mosquito-Borne Diseases webpage.

 

About MVCAC

The Mosquito and Vector Control Association of California (MVCAC) is the statewide voice for mosquito and vector control professionals. The association provides public health information, expertise, mosquito and vector-borne disease surveillance, innovative research, professional training, effective legislative and regulatory advocacy on behalf of California public agencies.