Americans are being warned about a surge in mosquito-borne dengue cases appearing across the country, raising the risk of a larger nationwide outbreak.
This year, a “higher than expected” number of infections has been recorded in the United States, with 2,241 cases detected compared to 3,036 in all of 2023.
And a record number of dengue infections have been detected in the Americas, where 9.7 million people have the virus, double the number from last year.
The World Health Organization says more than 4,000 people have died from the disease this year.
The map above shows the counties that recorded dengue cases between 2020 and 2023.
And this shows the number of travelers who arrived in the US with a dengue infection between 2010 and 2023. The numbers have increased in recent years.
The above shows the number of patients who tested positive for dengue despite not traveling outside the United States.
CDC warned of rebound in public health alert published today, saying many infections were linked to travelers returning to the US from countries where the disease is spreading rapidly.
But people are also becoming infected within the United States.
At least six cases of local transmission have been recorded in Florida – those in people who have not travelled recently – and there is an outbreak in Puerto Rico, with an emergency declared in the territory in March when the territory registered 1,500 infections.
There have also been previous small-scale outbreaks in Texas, Hawaii, Arizona and California.
The CDC warning comes as a number of previously nearly absent tropical diseases begin to return to the U.S., including malaria, which prompted alerts in Florida last year.
And it was issued just before the upcoming hotter summer months, when warmer weather typically causes dengue cases to rise.
In the alert, CDC officials wrote: ‘The global incidence of dengue in 2024 has been the highest on record for this calendar year; Many countries are reporting higher than usual numbers of dengue cases.
‘Summer travel to the United States often overlaps with peak dengue activity months in many countries.
“Epidemics in the Americas region increase travel-associated cases and limit local transmission in the continental United States.”
Of the dengue cases recorded in the United States this year, 745 have been in travelers (or those who tested positive after recently returning from abroad), which was “more than expected” for this time of year.
The photographs above show the symptoms of dengue rash. About one in four infected people suffer symptoms of the virus, including a rash.
The CDC did not reveal which countries people were returning from, but so far this year Brazil has the largest outbreak (with 6 million suspected dengue cases) along with the situation in the capital, Brasilia, so bad doctors said reminiscent of the early days of COVID-19.
Large outbreaks have also been recorded in Argentina (400,000 cases) and Paraguay (250,000), and so far this year other cases have been reported in 90 countries on six continents.
Dengue fever is not transmitted from person to person, but is transmitted through the bites of infected mosquitoes.
For someone to contract the disease locally, the area’s mosquito population must have contracted the virus, usually by biting an infected person who recently returned to the United States from abroad.
It could also be the case that infected mosquitoes have migrated to the area or arrived on boats or planes.
Dengue fever is endemic in many countries around the world, with countries in South America, Asia and Africa tending to report higher numbers of cases.
Dengue is a potentially deadly virus that is transmitted to people through infected mosquitoes and was historically known as “breakbone fever.”
It is transmitted by bites from infected mosquitoes, which transfer the virus to the patients’ bloodstream.
About one in four infected people develop symptoms five to seven days after a bite, including high fever, rash, muscle aches, joint pain and pain behind the eyes.
This has earned dengue the nickname “bone-breaking fever,” and sufferers say their joints and muscles can be so painful that they feel like their bones are breaking.
Of those who develop symptoms, one in 20 suffers from a severe form of the disease, which can cause bleeding, shortness of breath and shock.
Thirteen percent of patients die from the disease if they do not receive treatment.
There is no antiviral for dengue, nor drug to attack the virus, but the World Health Organization says that by quickly replacing lost fluids the mortality rate drops to less than one percent.
There is a dengue vaccine available and approved by the FDA for children ages nine to 16, but its manufacturer, French pharmaceutical giant Sanofi Pasteur, has discontinued production globally, citing lack of demand.
There are doses available in Puerto Rico, but they are expected to run out by 2026.
Dengue cases have increased in Latin America, which is believed to be related to the El Niño climate cycle at the time, which brings more heavy rain to areas of the continent, creating more standing water in which mosquitoes can multiply.
At the same time, rising temperatures have allowed mosquitoes to be active for longer each year and to move further north.
In areas of the world where outbreaks are not as common, the increases are partly related to travel, leading to people who become infected abroad entering the US and then being bitten by a mosquito, that transmits the virus to the insect and allows it to live. take root in the local mosquito population.
In Florida, where cases are being recorded in people who have not traveled abroad, residents are urged to empty containers of stagnant water near their homes, as they are breeding sites for mosquitoes.
The CDC also recommended that people take steps to prevent mosquito bites, including using insect repellent or long pants and shirts.
Emma Cox, 27, is one of those who claims to suffer from dengue. She had traveled to Indonesia, but 10 days after returning to the UK, she developed symptoms.
Ms Cox had been in Indonesia only 10 days before contracting dengue.
Authorities urged doctors to have a “heightened suspicion of dengue” among patients who had recently returned from a country with an outbreak.
Doctors were also urged to order appropriate diagnostic tests for the disease and to promptly report any new patients to state and national authorities.
It is typically tested by a PCR test performed on nasal swabs or blood samples. Other methods include an antibody test.
A young UK resident, Emma Cox, 27, became infected with dengue during a trip to Indonesia, but originally attributed her symptoms to the flu.
On the fifth day of her “dream” trip to Bali, she explained how she began to suffer from muscle and joint pain and a headache so severe she had to wear sunglasses while indoors.
On the tenth day, the pain became so intense that he booked an emergency flight home.
Shortly after landing in the UK, he developed a rash all over his body and went to A&E, where doctors diagnosed him with dengue.
“The virus gave me a rash that spread all over my body. I felt terrible and thought it would never go away,” she said.
Cox said there was a hole in the window of his hotel room in Bali and he woke up every morning with mosquito bites covering his body.