Health authorities in Los Angeles have issued a warning regarding an increase in dengue fever cases within the area among individuals who have not traveled outside the U.S. mainland. This comes a year after California reported its first case of locally acquired dengue fever. At least three people in the Baldwin Park neighborhood, east of downtown Los Angeles, have recently shown signs of being infected with dengue after mosquito bites.

Barbara Ferrer, the director of the Los Angeles County Department of Public Health, described the situation as an unprecedented cluster of locally transmitted dengue fever in a region where such cases have not previously been documented. Apart from Los Angeles, similar cases stemming from mosquito bites within the U.S. have been reported in Florida, the U.S. Virgin Islands, and Puerto Rico, which is currently facing a dengue epidemic.

Globally, dengue cases have been on the rise due to the impact of climate change, which has led to warmer temperatures, allowing mosquitoes to expand their habitat. While Aedes mosquitoes, the carriers of dengue fever, are prevalent in Los Angeles County, confirmation of local infections only occurred last year in Pasadena and Long Beach.

Aiman Halai, the head of the department’s Vector-Borne Disease Unit, noted that prior to these recent cases, instances of dengue in California were linked to individuals traveling to regions where the disease is widespread, like Latin America. In L.A. County alone, 82 cases have been reported this year from travelers returning from abroad, with a total of 148 cases across California.

Symptoms of dengue fever can include high fevers, rashes, headaches, nausea, vomiting, muscle pain, and joint pain. About a quarter of those infected will exhibit symptoms within a week of being bitten by a mosquito carrying the virus. Additionally, one in twenty individuals with symptoms may develop severe dengue, which can result in severe bleeding and be life-threatening.

To combat the spread of the virus, public health officials plan to conduct outreach within a 492-foot radius of affected individuals’ homes, which aligns with the flight range of the mosquitoes that transmit dengue fever. Residents are advised to use insect repellent and remove any standing water on their properties where mosquitoes can breed. Thus far, authorities have not detected any dengue-carrying mosquitoes in the San Gabriel Valley through ongoing testing efforts.