The district is investigating the first case of dengue in a patient with no travel history

The county health department is investigating what health officials suspect is the first locally transmitted case of dengue, the tropical disease whose transmission has recently increased nationwide.

An ongoing outbreak of the viral disease – often called dengue fever – across much of South America has led to a local increase in the number of travel-related dengue cases in San Diego County. However, local transmission is more worrisome because it suggests that a local mosquito bit an infected person and then transmitted that infection to a second person in the area.

Such a chain of transmission usually fizzles out on its own, but it can continue indefinitely if more mosquitoes feed on an infected person before their infection is detected. Out of an abundance of caution, health authorities often do everything they can to break possible chains of transmission.

To that end, the county's vector control program began hand-spraying mosquito-killing insecticides on Friday and worked through the weekend to treat a roughly 60-acre area west of Orange Glen High School in east Escondido, said to contain about 170 homes the neighborhood includes the infected individual living. Emergency services will begin spraying insecticides from trucks within an expanded radius on Monday.

The spraying work is expected to last until Thursday. Similar efforts recently occurred in Oceanside and the Mount Hope neighborhood of San Diego after travel-related dengue cases emerged.

Similar efforts were made in 2016 to prevent the Zika virus from gaining a foothold in a local mosquito population.

Dr. Ankita Kadakia, the county's interim health officer, said Sunday that she believes the overall risk of additional transmission is low.

The first local case of dengue in San Diego was so severe that it required hospitalization. The patient has now recovered to the point where he can recover at home, district officials said. They did not say whether the patient was male or female.

Symptoms of dengue infection generally appear four to seven days after a mosquito bite and include fever, chills, pain, nausea, vomiting and rash. Most people recover without significant medical consequences; However, some severe cases can cause fatal symptoms such as shock and shortness of breath.

Local transmission is not limited to San Diego County. Los Angeles County has reported five locally transmitted dengue cases so far this year, with Long Beach and Pasadena reporting their first cases in 2023.

Vector control experts are urging the public to do everything they can to eliminate mosquito hatching areas on their properties. The tiny Aedes aegypti mosquito that transmits dengue breeds in shallow pools of water, and a recent demonstration showed that backyard drains often contain enough moisture to breed swarms, even in the current dry season.

The county offers free mosquito control inspections for anyone concerned about ongoing infestations. Service requests can be made by email at [email protected] or by telephone at 858-694-2888.

Originally published: October 6, 2024 at 12:36 p.m