The Los Angeles County Department of Public Health (LACDPH) recently announced it is investigating the first case of locally acquired dengue fever in a resident of the San Gabriel Valley.
The infected person reported no history of travel to areas where the mosquito-transmitted dengue virus is endemic, such as Mexico or Central America.
As of October 15, 2025, the LACDPH stated ‘while the potential risk for widespread dengue virus transmission in Los Angeles County remains low, this case highlights the presence of infected mosquitoes locally and underscores the importance of preventive measures to control the spread of this virus.’
LA’s first confirmed case of locally acquired dengue was reported in September 2024.
During the 2024 mosquito season in LA County, between July and November, a total of 14 cases were confirmed, which is extremely rare for a region where mosquitoes had not previously transmitted the virus.
“Dengue is preventable, and community action is our strongest defense. Preventing mosquito bites and mosquito breeding is the best way to stop local transmission of dengue,” said Muntu Davis, MD, MPH, Los Angeles County Health Officer, in a press release.
“People should follow these simple steps to reduce their exposure to mosquitoes and risk for mosquito bites: 1) Use insect repellent on you and your family; 2) Remove items that hold standing water around your home where mosquitoes can lay eggs and breed; and 3) Use, install, or repair window and door screens to prevent mosquitoes from entering your home,” stated Dr. Davis.
The County stated San Gabriel Valley residents who have symptoms of dengue should see their healthcare provider, as a blood test is the only way to confirm dengue infection.
The San Gabriel Valley is located just east of the City of LA.
Similar to Florida, where local cases of dengue have been confirmed along the southeast coast in 2025, LACDPH urges healthcare providers to consider dengue in patients with acute febrile illness and test for and report suspect cases of mosquito-borne diseases.
As of October 19, 2025, dengue vaccines are only available in Puerto Rico and various countries outside the United States.
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