Earlier this year, the Centers for Disease Control and Prevention (CDC) issued a global travel notice for multiple countries due to escalating outbreaks of a mosquito-borne disease that can cause brain hemorrhages. The Level 1 travel advisory was released after detecting unusual increases in dengue fever cases worldwide. Specifically, the CDC warned of 16 countries where travelers face an elevated risk of contracting the illness, urging them to take precautions against mosquito bites.
Now, a new CDC report reveals a staggering 359 percent rise in average annual dengue cases in the United States in 2024 compared to the 2010-2023 annual average. In 2024, the most recent data available, a record 3,798 dengue fever cases were reported, up from the average of 828. Among these, 97 percent were travel-associated, while the remaining three percent—105 cases—were locally acquired. Of all patients, 36 percent were hospitalized, and three percent of cases were severe. There were six deaths.
Cases peaked from July to September, with Americans aged 50 to 59 comprising the largest share of patients at 22 percent. Travel-associated cases primarily originated from the Caribbean, accounting for 34 percent of cases, including the US territories Puerto Rico and the US Virgin Islands.
The CDC report stated: 'The sharp increase in travel-associated dengue highlights an urgent need for enhanced prevention strategies, improved clinical awareness, and tailored messaging for travelers to areas with ongoing dengue transmission.'
Dengue fever is spread when a person is bitten by an infected Aedes aegypti mosquito. In some patients, it can trigger life-threatening health complications such as internal bleeding, respiratory distress, and heart failure.
The global dengue travel advisory is continuously updated. Countries currently on the list as reporting higher-than-usual numbers of infections include Bangladesh, Bolivia, Colombia, Cook Islands, Guyana, Maldives, Mali, New Caledonia, Samoa, Somalia, Timor-Leste, and Vietnam.
Dengue is present in more than 100 countries worldwide and poses a year-round threat to travelers and local residents in high-risk areas. A Level 1 travel advisory urges Americans to practice usual precautions due to the presence of an outbreak. It is the lowest level of travel alert among four possible levels, with Level 4 advising against all travel.
Dengue fever, spread by the Aedes aegypti mosquito, often causes asymptomatic infection, but in some patients it can lead to life-threatening internal bleeding, respiratory distress, and heart failure. It can also cause shock and organ failure, particularly of the liver, brain, and heart. Patients may develop dengue shock syndrome, where severe bleeding causes a rapid drop in blood pressure and shock.
Children under five, adults over 65, and pregnant women are considered most at risk. Dengue was virtually eradicated from the US in the 1970s, but sporadic outbreaks have occurred since, especially in warmer states like Florida and California. Most US cases are linked to international travel.
According to the CDC report, 24 percent of cases stemmed from North America, and nearly 16 percent were from travel to Central America. The report stated: 'These findings underscore the urgent need for enhanced prevention strategies, clinical awareness, and tailored public health messaging for travelers to areas where dengue is endemic.'
The rise in travel-associated cases could increase the risk of local transmission in parts of the US that typically do not see dengue. The report found that Florida had the highest number of dengue cases in 2024, with 1,044 cases, followed by California (720), New York (338), and Texas (241). Locally acquired cases were reported in Florida (85), California (18), and Texas (2).
Health officials estimate that 40 to 80 percent of people infected with dengue fever do not develop symptoms. When symptoms do appear, they typically occur abruptly about five to seven days after infection. Warning signs include a fever above 100°F (38°C), severe headache, pain behind the eyes, bone, joint or muscle pain, and bleeding in the gums. Some patients also develop a rash several days after a high fever. In severe cases, patients may experience severe abdominal pain, persistent vomiting, and lethargy.
There is no specific cure for dengue fever; treatment consists of supportive care and therapies to manage symptoms and complications. Doctors recommend that patients with mild symptoms drink plenty of fluids and take acetaminophen (Tylenol) to ease pain. In severe cases, patients may be hospitalized for supportive care, intravenous fluids, blood pressure monitoring, and blood transfusions.
A three-dose vaccine is available for children aged nine to 16 years, which reduces the risk of symptomatic infection by about 80 percent.
