LA County Logs Fourth Case of Locally Acquired Dengue

A fourth case of locally acquired dengue has been reported in California, according to a press release from the Los Angeles County Department of Public Health. The affected individual, a resident of the Panorama City neighborhood, had no history of travel to endemic areas, and this most recent case is not related to the previous cases reported by the LA County Department of Public Health on September 18, 2024. The first case was reported on September 9, 2024.

The local transmission of dengue in Los Angeles County is “unprecedented,” said Muntu Davis, MD, Los Angeles County health officer, in the press release. Davis emphasized previous recommendations to the public to protect themselves including using insect repellant, eliminating standing water, and securing screens on doors and windows to keep mosquitoes away.

Clinicians are advised to remain vigilant to dengue in patients with acute febrile illness and to test for dengue and report cases of suspected mosquito-borne illness, according to the press release. Symptoms can include fever, severe headache, pain behind the eyes, pain in the joints and muscles, rash, and mild bleeding. Healthcare providers also should routinely discuss mosquito bite prevention with patients and travelers.

According to the Centers for Disease Control and Prevention (CDC), approximately one quarter of dengue infections are symptomatic. Signs of progression to severe disease include abdominal pain or tenderness, persistent vomiting, clinical fluid accumulation, mucosal bleeding, lethargy or restlessness, and liver enlargement.

The CDC offers guidance for clinicians on clinical care for patients with dengue, as well as clinical diagnosis and testing.

Stay Alert to Potential Dengue Drivers

“While the risk of locally acquired dengue likely remains quite low in the LA area, clinicians should now be on alert about the prospect and patients presenting with a consistent syndrome and no confirmed alternative diagnosis should be tested,” said James Lawler, MD, associate director for International Programs and Innovation at the Global Center for Health Security and professor in the Infectious Diseases Division at the University of Nebraska Medical Center, Omaha, Nebraska, in an interview.

“I am honestly impressed that we have been able to identify multiple cases without known risk factors of travel to known endemic areas,” Lawler said.

Asked what might be driving the recent cases, “I think it is a combination of escalating intensity of dengue transmission in many endemic areas outside the US, which creates a scenario of more travelers arriving in the US with active dengue, and increased numbers of mosquitoes locally able to transmit the virus,” Lawler told Medscape Medical News.

Dengue is very common in the Caribbean, Central and South America, Southeast Asia, and all the tropics, which are all places with a high travel volume to the United States, he said.

The climate also may play a role, Lawler noted. “I think LA has seen more rainfall over the last 2 years compared to previous years and that increases mosquito populations,” he said. “Mosquito control is the key to limiting the establishment of dengue as an endemic disease in the US, and we need more investment in vector control programs and the public health infrastructure that keeps us safe,” he emphasized.

Looking ahead, Lawler said that more locally acquired dengue cases are not unlikely. “Past is often prologue, so I would not be surprised if we see more cases pop up,” he told Medscape Medical News. “I think winter and spring are typically wetter in Southern California, so that will probably mean more mosquitos and higher risk,” he noted.