Dengue Is Surging, Including in the Americas

By Stan Deresinski, MD, FACP, FIDSA

Clinical Professor of Medicine, Stanford University

SYNOPSIS: Dengue is surging, and cases have been acquired in the United States, including in Puerto Rico and Florida.

SOURCE: Centers for Disease Control and Prevention. CDC Heath Advisory. Increased risk of dengue virus infections in the United States. June 25, 2024. emergency.cdc.gov/han/2024/han00511.asp

The recorded global incidence of dengue is the highest ever. In all of 2023, the Pan American Health Organization (PAHO)/World Health Organization (WHO) recorded 4,617,108 cases of dengue in the Region of the Americas, but this number doubled to 9,386,082 in just the first 23 weeks of 2024.¹ Among the 43 countries reporting during that time, Brazil (where the clinically indistinguishable Oropouche fever also is surging) accounted for 7,866,769 (83.8%) cases, a 230% increase over those occurring in the first half of 2023. Puerto Rico, with 4,968 cases, has declared a public health emergency, and vaccination has been implemented. In relatively nearby Key West, FL, two locally acquired cases have been reported.²

While the vast majority of cases in the United States are associated with travel, a tiny proportion are locally acquired, thus raising concern about dengue virus becoming embedded in our mosquito populations. The acquisition of dengue in Florida is not a novel phenomenon. After near total absence of autochthonous cases in Florida for 75 years, 88 cases “associated with” Key West were recorded in outbreaks in 2009-2010. In 2023, 10 autochthonous cases have been reported from four Florida counties, including Monroe County, in which 99% of the population reside in the Florida Keys. Among the 10 cases, two occurred in Key West and six occurred in adjacent Miami-Dade County. At the same time, 24 imported cases were identified in Florida travelers.

In California, there were 48 cases of dengue recorded in the first six months of 2024, none of which were locally acquired.³ However, in 2023 there were two authochthonous cases — one in Pasadena and one in Long Beach. These were the only locally acquired cases in at least seven years.

COMMENTARY

The marked increase in worldwide dengue incidence, which likely is related to global warming, is of obvious concern. Clinicians must be aware of consistent signs, symptoms, and epidemiological history of dengue, thus allowing early diagnosis, which may be confirmed by RT-PCR, NS1 antigen detection, and/or immunoglobulin M (IgM) antibody tests. Unfortunately, there is no available specific antiviral therapy for dengue, but supportive therapy, as indicated, should be used. Clinicians must be attentive to early signs of the onset of dengue hemorrhagic fever and rapidly initiate the WHO-recommended standardized fluid replacement strategy in those with severe disease and in danger of progression and also monitor for hemorrhagic manifestations.

The key to dealing with dengue is its prevention. One vaccine, Dengvaxia, is not approved for use in U.S. short-term travelers to dengue-endemic areas. At any rate, Dengvaxia is only approved for use in children 9 through 16 years of age of who have a previous history of laboratory-confirmed dengue infection (a risk for development of hemorrhagic fever with subsequent infection) and reside in dengue-endemic regions. In addition, its lack of use has led Sanofi to discontinue its manufacture — the remaining doses will expire in 2026. Two other vaccines are not available in the United States.

That leaves avoidance of mosquito bites as the critical approach to prevention. Water should be emptied from containers around residences to eliminate sites where mosquitoes lay their eggs. Effective screening is critical. Individuals should wear loose-fitting, long-sleeved shirts and pants and also use insect repellent. Permethrin can be applied to clothing.

REFERENCES

Pan American Health Organization. Epidemiological Update – Increase in dengue cases in the Region of the Americas — 18 June 2024. https://www.paho.org/en/documents/epidemiological-update-increase-dengue-cases-region-americas-18-june-2024
Florida Arbovirus Surveillance. Week 26: June 23-29, 2024. https://www.floridahealth.gov/diseases-and-conditions/mosquito-borne-diseases/_documents/2024-26-arbovirus-surveillance.pdf
California Department of Public Health. CPH monthly update on number of dengue infections in California, July 1, 2024. https://www.cdph.ca.gov/Programs/CID/DCDC/CDPH%20Document%20Library/TravelAssociatedCasesofDengueVirusinCA.pdf