In response to the alarming rise of dengue cases across the globe, U.S. health officials have issued a warning to doctors, urging them to be on high alert for the tropical disease. Dengue, a virus transmitted by mosquitoes, has seen a significant increase in countries in the Americas, with new records being set for dengue cases in just six months.

Climate change has been identified as a contributing factor to the surging spread of the virus. The World Health Organization declared a global emergency in December, while Puerto Rico declared a public health emergency in March due to the severity of the situation. Although dengue remains relatively less common in the continental United States, there has been a notable increase in cases compared to the same period last year, primarily stemming from infections acquired during travel abroad.

While health officials emphasize that there is currently no evidence of a local outbreak, they do highlight the potential threat posed by local mosquitoes. Consequently, the Centers for Disease Control and Prevention (CDC) has issued a health alert advising doctors to familiarize themselves with the symptoms of dengue, inquire about recent travel histories of patients, and consider ordering dengue tests when appropriate.

Dengue is caused by a virus spread by a specific type of mosquito typically found in warm weather regions. Climate change has facilitated the expansion of this mosquito's geographic reach. Most infected individuals do not exhibit symptoms, but those who do may experience headaches, fever, and flu-like symptoms. Severe cases can involve serious bleeding, shock, and even death. Of particular concern are repeated infections, as the antibodies developed in response to one type of dengue may fail to neutralize a second type, potentially aiding the virus in entering immune cells and replicating.

In Puerto Rico, where exposure to dengue type 1 has been prevalent for over two decades, health authorities have observed an increase in cases caused by dengue types 2 and 3. Last month, the island recorded its first dengue-related death of the year. With no widely available medicine or broadly-used vaccine for treating dengue infections, concerns regarding the disease's impact continue to grow.

Sanofi Pasteur, a pharmaceutical company, produced a three-dose vaccine recommended by U.S. officials in 2021 for children aged 9 to 16 who had previous laboratory evidence of dengue infection and resided in regions with high dengue prevalence, such as Puerto Rico. However, due to limited usage and other complications, Sanofi Pasteur has announced that it will discontinue the vaccine, leaving only a vaccine made by Tokyo-based company Takeda that is not currently licensed in the U.S.

Globally, over 6.6 million dengue infections were reported across approximately 80 countries last year. The first four months of this year have seen 7.9 million cases and 4,000 deaths, with particularly high numbers in Brazil and Peru. In the United States, there were around 3,000 cases of dengue reported in 2021 in states and territories, making it the worst year for the disease in a decade. Notably, approximately 180 cases occurred locally in Florida, Texas, and California. This year, Puerto Rico has reported nearly 1,500 locally acquired cases, while most cases in the continental U.S. remain tied to international travel.

The increasing prevalence of dengue poses not only a health risk but also an economic concern, as outbreaks in countries may deter tourists. Dr. Lulu Bravo, a specialist in pediatric tropical diseases at the University of the Philippines Manila, emphasized that the situation is a "traveler's nightmare" and a growing international issue.

With dengue cases surging worldwide and raising concerns across various nations, health officials stress the urgency of continued vigilance, prevention, and management strategies to mitigate the impact of this tropical disease.