Tejal Somvanshi
The Centers for Disease Control and Prevention (CDC) has issued a Health Alert Network notice highlighting the continued risk of dengue virus infections in the United States and globally. The alert comes as dengue activity remains high in U.S. territories and many countries report unprecedented case numbers.
Record-Breaking Numbers
The Americas witnessed alarming statistics in 2024, with 13 million dengue cases and 8,200 deaths. As of March 2025, global cases have already surpassed 760,000 – a 15% increase compared to the previous five-year average.
“This trend is expected to continue with increased dengue activity in endemic areas in 2025,” the CDC warns in its latest advisory.
In 2024, a record 3,483 travel-associated dengue cases were identified among U.S. travelers, representing an 84% increase compared to the previous year. Florida (1,016), California (648), and New York (327) reported the highest numbers of these travel-related cases.
U.S. Territories Under Emergency Orders
The situation remains particularly concerning in U.S. territories:
- In Puerto Rico, dengue cases have stayed above outbreak threshold since February 2024, with a public health emergency declared in March 2024 still in effect. The territory reported 6,291 cases last year, with over 52% (3,292) requiring hospitalization and 13 deaths. As of March 7, 2025, 936 cases have already been reported – a 113% increase compared to the same period in 2024.
- The U.S. Virgin Islands declared a dengue outbreak in August 2024 that remains active. Officials identified 208 locally acquired cases in 2024, with 30 more reported in early 2025.
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Local Transmission in Continental U.S.
Beyond travel-associated cases, the continental United States saw locally acquired dengue in Florida (91 cases), California (18 cases), and Texas (1 case) during 2024.
The CDC notes that spring and summer travel coincides with peak dengue seasons in many countries, increasing both travel-associated and local transmission risks in areas with competent mosquito vectors.
Changing Serotypes Add Complexity
All four dengue virus serotypes were found among travelers returning to the U.S. in 2024. While DENV-3 was most common throughout the year, DENV-4 has been increasing in recent months, identified in 50% of travel-associated cases with available serotype data between October 2024 and January 2025.
The CDC warns that introductions of new serotypes have been associated with larger outbreaks and potentially more severe clinical outcomes in patients with previous dengue exposure.
Testing Recommendations
The CDC emphasizes using the DENV-1-4 real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay for accurate diagnosis when dengue is suspected. Healthcare providers are advised to test patients with RT-PCR or NS1 antigen tests alongside IgM antibody testing.
These testing recommendations remain important regardless of symptom onset, though RT-PCR and NS1 antigen tests become less sensitive after the first week of symptoms.
The health agency continues to support state, tribal, local, and territorial public health partners in surveillance and response to this ongoing threat.
