Spring breakers are being warned over a fast-spreading disease that could be life-threatening.
In an emergency notice, the CDC raised the alarm over dengue fever — saying the US and Americas region is seeing high transmission, with nearly 1,000 cases reported across 21 states already this year.
A record number of infected travelers – nearly 4,000 – returned to the US in 2024.
And just as the spring travel season kicks off, popular destinations like the US Virgin Islands, Puerto Rico and Mexico, are experiencing high transmission of the illness, with Mexico recording 20,000 cases already this year.
The disease is spread when infected mosquitoes bite people, and it causes fever, headache and rash in most cases.
In severe cases, the disease develops into dengue shock syndrome, which can trigger heavy bleeding from the nose, gums or under the skin and pain behind the eyes.
It is rare for dengue to turn into a severe disease, but when it does about one in 100 patients do not survive. This rises to 20 percent if someone does not get treatment.
There’s no specific medicine for dengue fever, with treatment instead relying on keeping patients hydrated and relieving pain.
The CDC issued a warning to avoid mosquito bites, such as wearing insect repellent and long-sleeved clothing and told doctors to be ‘suspicious’ for the virus in patients who had recently returned from abroad and were suffering from a high fever.
Just as the spring travel season kicks off, popular destinations like the US Virgin Islands, Puerto Rico and Mexico , are experiencing high transmission of dengue fever
In the emergency notice, officials said: ‘Dengue virus transmission remains high in the Americas region, including in the U.S. territories of Puerto Rico and the U.S. Virgin Islands.
‘Spring and summer travel coincide with the peak season for dengue in many countries, increasing the risk of both travel-associated and locally acquired cases in the United States.’
About 173million Americans travel for spring break in March and April.
In Puerto Rico, infections have surged this year compared to the same period last year — with 861 cases already recorded.
In the US Virgin Islands, 30 people have already tested positive for the disease.
Across the US, 985 cases of dengue fever have been reported in 24 states and jurisdictions.
And there have been 97 cases reported in the continental US associated with travel.
Florida has reported the most cases at 42, followed by California with 10 cases and New York with six cases.
It was not clear where the infected travelers had returned to the US from.
The CDC said in its alert: ‘This trend is expected to continue with increased dengue activity in endemic areas in 2025.’
Dengue cases in travelers returning to the US surged in 2024, with officials fearing this year could be no different
There was also an uptick in locally-acquired infections, particularly in Florida and California
The above map shows states where dengue fever has been detected in travelers so far this year
Experts say dengue cases are rising due to the El Niño phenomenon — which leads to unusually hot sea surface temperatures causing more rainfall and a longer mosquito breeding season in the Americas.
Climate change leading to longer periods of warmer weather is also thought to be driving the increase in cases and allowing mosquitoes to spread to new areas.
Officials warn approximately just one in four dengue patients are symptomatic, with their infection diagnosed via a PCR test.
The virus is particularly dangerous for infants under one year old, pregnant women and adults over 65 years old.
Worldwide, there were 13million cases reported in 2024, nearly three times the tally for 2023, and 8,200 deaths, up 240 percent over the previous 12 months.
As of March 6 this year, there were 760,000 dengue cases globally — a 15 percent increase compared to the five-year average.
