ESCONDIDO, Calif. (FOX 5/KUSI) -- The San Diego County Health Department is investigating the first-ever case of locally acquired dengue fever after an Escondido resident fell ill without a recent history of travel to endemic areas. To safeguard public health, County Vector Control launched an emergency spraying operation this weekend, targeting about 170 homes in Escondido. The treatments, which began on Friday and will continue through Thursday, aim to reduce the mosquito population and curb the potential spread of the dengue virus, the county explained. Dengue fever, a tropical viral illness, is typically transmitted through the bites of infected mosquitoes. While there have been 49 cases of travel-related dengue reported in San Diego County this year, the emergence of a locally acquired case raises concerns. Hotel Del Coronado workers vote ‘yes’ to authorize strike: what this means Dr. Ankita Kadakia, the county's interim public health officer, stated, “While the risk of widespread transmission of dengue remains low in San Diego County, County Public Health and Vector Control are working closely to respond quickly to prevent mosquitoes from spreading the illness in this area.” The appearance of locally acquired dengue in San Diego is not entirely unexpected. Recently, Los Angeles County reported five locally contracted dengue cases, with Long Beach and Pasadena noting their first cases in late 2023. In response to the increasing mosquito population and recent travel-related cases, Vector Control conducted similar treatment efforts in Oceanside in September and in the Mount Hope area of San Diego in July. These actions were taken as preventative measures to mitigate the risk of local transmission. Have you seen the ‘Ghosts in the Machine’ mural in La Jolla? Dengue symptoms typically manifest four to seven days after a bite from an infected mosquito and include fever, chills, body aches, nausea, vomiting and rash. While most cases resolve within a week, severe cases can lead to hospitalization, shock and respiratory distress. To prevent mosquito-borne illnesses, the county encourages residents to eliminate standing water in and around their homes, use EPA-approved insect repellents, and wear long sleeves and pants when outdoors. Additionally, residents can obtain free mosquitofish to help control mosquito breeding in stagnant water sources. For more information on dengue fever and preventative measures, residents are advised to contact County Public Health or visit the county's official health website.