Florida reports highest locally acquired dengue cases in 100 years

The CDC issued a Level 3 emergency response on October 22, 2026, as Florida reported 425 locally acquired dengue cases across 11 counties, marking the state's largest outbreak since the 1930s. Transmission has been driven by expanding vector mosquito populations and recent hurricane rainfall, with 47% of patients requiring hospitalization. With no licensed vaccine available in the United States, medical management relies on supportive care and mosquito control.

Florida dengue case counts

• ▪Hillsborough County recorded 346 locally acquired dengue cases and Pinellas County recorded 51 cases as of October 17, 2026
• ▪Florida recorded 650 total locally acquired dengue cases during the 15-year period from 2010 to 2025
• ▪Florida reported 425 locally acquired dengue cases across 11 counties as of October 17, 2026, marking the largest outbreak in the state since the 1930s

Characteristics of the Florida outbreak

• ▪Approximately 47% of individuals infected in the 2026 Florida dengue outbreak required hospitalization
• ▪Dengue virus serotype 2 was the predominant virus type identified in the 2026 Florida dengue outbreak

Florida mosquito control and weather factors

• ▪Hillsborough, Pinellas, and Pasco counties in Florida repeatedly extended local states of emergency in 2026 to fund aerial spraying against mosquito larvae
• ▪Recent hurricane-related rainfall in 2026 contributed to ongoing domestic dengue transmission risks in Florida, according to CDC NCEZID director Chris Braden

CDC emergency response activations

• ▪The CDC deployed an Epi-Aid team to assist the Republic of the Marshall Islands after the territory declared a state of emergency on Ebeye and Majuro
• ▪The October 2026 dengue response represented the CDC National Center for Emerging and Zoonotic Infectious Diseases' eighth emergency activation of 2026
• ▪The CDC issued a Level 3 emergency response for dengue outbreaks in Florida and the Republic of the Marshall Islands on October 22, 2026

Mosquito expansion and cases in other states

• ▪Aedes aegypti mosquitoes expanded their range north into Virginia, while Aedes albopictus reached into Pennsylvania
• ▪Virginia reported its first locally acquired dengue case in 2026, while Texas, California, Arizona, and Hawaii reported zero locally acquired cases in 2026

Dengue symptoms and severe risk factors

• ▪Between 20% and 40% of dengue-infected individuals develop symptoms, beginning with an abrupt febrile phase lasting two to seven days
• ▪Older adults, pregnant individuals, and patients with pre-existing conditions like diabetes or hypertension face higher risks of severe dengue
• ▪Approximately 5% of symptomatic dengue patients progress to severe dengue, marked by plasma leakage, shock, respiratory distress, and organ damage
• ▪Warning signs of severe dengue progression include severe abdominal pain, persistent vomiting, mucosal bleeding, fluid accumulation, and rising hematocrit levels

Dengue treatment guidelines

• ▪Supportive management, including intravenous fluid administration and strict fluid tracking, serves as the primary treatment for dengue patients
• ▪CDC guidelines instruct clinicians to avoid administering nonsteroidal anti-inflammatory drugs, corticosteroids, intramuscular injections, or prophylactic platelets to dengue patients

Dengue vaccine availability

• ▪There is no licensed dengue vaccine available in the United States as of October 2026
• ▪Sanofi Pasteur's dengue vaccine increased severe disease risks in dengue-naive individuals through antibody-dependent enhancement
• ▪Takeda withdrew its U.S. biologics license application for its dengue vaccine in 2023 following discussions with regulators regarding data collection