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Washington, D.C. – U.S. health officials on Tuesday issued an urgent alert to doctors across the country, urging them to be vigilant for signs of dengue fever as the mosquito-borne disease reaches unprecedented levels globally. The Centers for Disease Control and Prevention (CDC) highlighted the necessity for heightened awareness among healthcare providers, given the alarming rise in dengue cases worldwide.
Global Surge Linked to Climate Change
Dengue, a viral infection transmitted by Aedes mosquitoes, has seen a dramatic increase in incidence, with climate change playing a significant role in its spread. Within the first six months of this year, several countries in the Americas have already surpassed previous annual records for dengue cases. This spike prompted the World Health Organization (WHO) to declare an emergency in December, followed by Puerto Rico’s public health emergency declaration in March.
Increased Cases in the U.S.
While dengue remains relatively rare in the continental United States, the CDC reports a threefold increase in cases this year compared to the same period last year. The majority of these cases involve travelers returning from regions where dengue is more common. However, local mosquitoes are also a potential threat, and there is no evidence of an ongoing outbreak within the mainland U.S.
CDC’s Health Alert
In its recent health alert, the CDC emphasized the importance of recognizing dengue symptoms, which can range from mild fever and flu-like symptoms to severe complications such as serious bleeding, shock, and death. Doctors are advised to inquire about patients’ travel histories and consider dengue testing when necessary.
“Dengue is a traveler’s nightmare and a growing international concern,” said Dr. Lulu Bravo, a pediatric tropical diseases expert at the University of the Philippines Manila, who has collaborated with pharmaceutical companies on dengue vaccines.
Complexities of Dengue Infections
The dengue virus has four distinct serotypes, and immunity to one type does not protect against the others. In fact, subsequent infections with different serotypes can lead to more severe illness. This phenomenon poses a significant challenge, particularly in regions like Puerto Rico, where type 1 dengue has been prevalent for decades. Recently, Puerto Rico reported its first dengue-related death of the year amid a rise in cases of dengue types 2 and 3, for which the population has little immunity.
“We’re currently seeing increases in the cases due to dengue 2 and dengue 3, for which the population has very little immunity,” said Dr. Gabriela Paz-Bailey, head of the CDC’s dengue branch in Puerto Rico.
Challenges in Treatment and Vaccination
There is currently no widely available medication for treating dengue infections. Vaccination efforts have also faced hurdles. The Sanofi Pasteur vaccine, approved in the U.S. in 2021, is designed to protect against all four dengue types but is recommended only for children aged 9 to 16 who have previously been infected with dengue and live in endemic areas like Puerto Rico. Due to these limitations, uptake has been low, with only about 140 children vaccinated in Puerto Rico since its introduction. Moreover, Sanofi Pasteur plans to discontinue the vaccine.
Another vaccine by the Japanese pharmaceutical company Takeda is not yet licensed in the U.S., though it shows promise. Other vaccines are still under development.
A Growing Concern in the Americas
Globally, dengue cases have surged dramatically. In 2023, over 6.6 million infections were reported by about 80 countries. This year, the numbers have already surpassed 7.9 million cases with 4,000 deaths reported in just the first four months, according to the WHO. The Americas, including Brazil and Peru, have been particularly hard-hit.
In the United States, last year saw about 3,000 dengue cases, the highest in a decade, with local transmissions recorded in Florida, Texas, and California. This year, nearly 1,500 locally-acquired cases have been reported, predominantly in Puerto Rico.
Conclusion
As dengue fever continues to surge globally, U.S. health officials stress the importance of vigilance among healthcare providers to identify and manage cases effectively. While most infections in the continental U.S. remain travel-related, the potential for local transmission remains a concern, underscoring the need for ongoing awareness and preparedness.
