County investigates first ever dengue case in patient with no travel history

The county health department is investigating what public health officials suspect is the first ever locally transmitted case of dengue, the tropical disease that has recently seen an uptick in transmission nationwide.

An ongoing outbreak of the viral illness — often called dengue fever — in much of South America has caused a local increase in the number of travel-related dengue cases detected in San Diego County. However, local transmission is more concerning, because it suggests that a local mosquito bit an infected person and then carried 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 additional mosquitoes feed on an infected person before their infection is detected. Public health departments often do what they can to interrupt any possible chain of transmission out of an abundance of caution.

Toward that end, the county’s Vector Control Program began hand spraying mosquito-killing insecticide Friday, working through the weekend to treat a roughly 60-acre area just west of Orange Glen High School in east Escondido said to encompass about 170 homes in the neighborhood where the infected individual lives. Crews will begin spraying insecticide from trucks within an expanded perimeter on Monday.

Spraying is expected to continue through Thursday. Similar efforts have recently occurred in Oceanside and the Mount Hope neighborhood in San Diego after travel-associated dengue cases popped up.

Similar efforts were undertaken in 2016 in an effort to keep the Zika virus from gaining a foothold in a local mosquito population.

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

San Diego’s first local dengue case was severe enough to require a hospital stay, county officials said. The patient has now recovered enough to convalesce at home. They did not say if the patient was male or female.

Symptoms of dengue infection generally appear four to seven days after a mosquito bite and include fever, chills, aches and pains, nausea, vomiting and rash. Most people recover without significant medical consequences; however, some who suffer severe cases can experience deadly symptoms such as shock and respiratory distress.

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

Vector control experts urge the public to do what they can to eliminate mosquito-hatching areas on their properties. The tiny aedes aegypti mosquito that carries dengue reproduces in shallow pools of water, and a recent demonstration showed that backyard drains often hold moisture sufficient to hatch swarms even during the current dry season.

The county offers free mosquito abatement inspections for anyone concerned about an ongoing infestation. Requests for service can be made by emailing vector@sdcounty.ca.gov or by calling 858-694-2888.

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