As Southern California reels from the devastation of the 2025 wildfires, another crisis is quietly and predictably emerging in the charred aftermath — thousands of neglected, debris-filled swimming pools are becoming prime breeding grounds for disease-carrying mosquitoes, sparking new public health concerns.
According to Jason Farned, district manager with the San Gabriel Valley Mosquito and Vector Control District (SGVMVCD), January’s blaze left behind “thousands of unmaintained swimming pools, damaged septic systems and debris-filled areas — ideal conditions for mosquitoes to grow. Cooler weather has temporarily suppressed mosquito activity, but that will change quickly as we move further into spring.”
Many residents don’t know when or if their pools can be restored to a safe condition, so the San Gabriel Valley Mosquito and Vector Control District — a district that spans 26 cities in Southern California, including Altadena and Pasadena — is stepping in to provide guidance and support.
Anais Medina Diaz, a vector control district spokesperson, said that officials have identified about 2,700 potentially concerning ashfilled swimming pools in the area, — about 1,300 pools inside the burn zone and about 1,400 on its perimeter. And that number doesn’t necessarily count septic tanks and ponds that weren’t identified during aerial surveillance.
A single swimming pool can provide a breeding ground for more than 3 million mosquitoes in a month, Diaz, said, “So our district has started to go out in the field to spray these pools particularly around the perimeter of the burn area to reduce the risk of mosquito transmitted diseases.”
For homeowners with pools, SGVMVCD is offering mosquito control services to property owners in the fire-impacted areas. Services include financial relief and targeted mosquito management to help prevent the spread of disease. Treatments may include the application of temporary mosquito control measures such as larvicides, other mosquito control products, or, when appropriate, the introduction of mosquitofish.
Property owners with damaged pools are encouraged to submit a request for mosquito control services, which will begin a direct communication with SGVMVCD.
Financial relief will be available to eligible property owners: Through a partnership with Los Angeles County, property owners will receive a waiver of SGVMVCD tax assessment charges for the 2024/2025 fiscal year under the county’s Direct Assessment Disaster Relief Program. For those who have already made payments, refunds will be issued. For more information about this program, property owners can click here to visit the Los Angeles County Property Tax Website.
The SGVMVCD has emphasized the need for pools to be either “Clean and Functional” or “Empty and Dry” to reduce the risk of mosquito-borne diseases.
“We’re really trying to focus on pools on the perimeter and work our way inward,” Diaz said, “because we want to make sure that the pools https://www.propertytax.lacounty.gov/ https://www.propertytax.lacounty.gov/ https://www.propertytax.lacounty.gov/
that are closest to communities that still have folks in them are not breeding or growing more mosquitoes and increasing the risk of disease transmission.”
Mosquitos are soon expected to become an issue in the coastal Pacific Palisades area as well, but vector control officials are trying to focus on inland areas first, because temperatures tend to rise earlier there than along the coast.
For homeowners with fire-affected swimming pools in the Southern California coastal areas, the Los Angeles County West Vector Control District expects to be providing support during the summer “Swimming pools in the Palisades fire area are definitely a concern with regards to mosquito breeding,” said Executive Director Aaron Arugay. “Our district will be responding throughout the summer to all requests for service regarding unmaintained pools in the Palisades fire area.”
Both SGVMVCD and LosAngeles County West Vector Control District said there is no additional cost to
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property owners for requesting inspections or treatment.
Officials expect that mosquito prevention efforts will be expensive: The first round of treatment alone will be about $306,000, and the Eaton fire zone will need at least two additional treatments this year. SGVMVCD collects only $20 per parcel each tax year, so additional mosquito remediation funds will be needed from the county, state, or reimbursements from the Federal Emergency Management Agency.
But the risk of mosquito-borne disease could be high if left unchecked. In a normal year, mosquitos already bring a real threat of disease to Southern California residents.
In 2024, there were 35 confirmed casesofWestNileVirusinL.A.County, including 27 hospitalizations and two deaths, according to data from the L.A. County Department of Public Health.
Dengue is another virus that is spread by mosquitoes. In 2024, L.A. County documented 234 cases of dengue infection last year.
Although many of those cases were travel-related, officials warn that warming temperatures are giving rise to local cases.
The flight range of most common mosquitos is about a mile, and officials warn that those in or travelling to the Eaton fire zone should be concerned about potential disease transmission, including the West Nile virus.
Mosquito control measures are nothing new for vector control districts after a wildfire, but Diaz said the sheer scale of this year’s devastation will make the challenge far greater.
