Dengue Detected in Southern California

During the global outbreak of dengue fever in 2023, most locally acquired cases in the continental United States have been confirmed in the State of Florida.

However, California reported on October 20, 2023, that the Pasadena Public Health Department (PPHD) reported a case of dengue in a Pasadena resident who did not travel outside the U.S. this year.

This is the first confirmed case of dengue in California not associated with travel.

Although Pasadena is home to the Aedes mosquito, dengue is not endemic in California.

According to the U.S. CDC, the state of California has reported 38 travel-related dengue cases in 2023.

To better understand the significance of this event, the San Gabriel Valley Mosquito and Vector Control District has deployed traps to assess the mosquito population. Importantly, testing to date has not identified any Dengue-infected mosquitos.

"PPHD has been conducting surveillance and investigation of mosquito-borne diseases in Pasadena for years," stated Dr. Matthew Feaster, PPHD Epidemiologist, in a press release.

"Our work so far, in partnership with the Vector Control District, gives us confidence that this was likely an isolated incident and that there is a very low risk of additional dengue exposure in Pasadena."

Pasadena is home to about 135,000 residents and is located northeast of Los Angeles, with over 3.8 million residents.

The city of Pasadena is also home to the Rose Bowl Stadium, which hosts numerous events, such as college football games.

Across the U.S., Florida's southeast coast has reported 366 travel-associated and 68 locally acquired dengue cases as week #41 in 2023.

The Florida Health Department reported that both Miami-Dade and Broward Counties remain under a mosquito-borne illness alert.

The CDC says dengue is a vaccine-preventable disease available in the U.S. While there is one approved dengue vaccine, it requires pre-admission testing.

In addition to vaccination, a first-in-class oral antiviral is in development to treat dengue.

On October 20, 2023, the Janssen Pharmaceutical Companies announced promising data from a Phase 2a human challenge study evaluating JNJ-1802; the data showed that the compound induced antiviral activity against dengue (DENV-3) in humans, compared to placebo, and is safe and well-tolerated. 

This experimental compound has advanced to a community-based field study to establish efficacy against circulating dengue serotypes in a real-world setting.