Increased risk of dengue virus in US, CDC warns – here’s what to know

FILE - A member of Municipal Civil Protection releases smoke with a fumigation machine in a park between the buildings during a fumigation campaign against the Aedes aegypti or Aedes albopictus mosquito, which is the transmitter of the dengue virus,

U.S. health officials are warning of an increased dengue virus risk, as cases of the mosquito-borne viral disease hit record numbers in other parts of the world. 

The U.S. Centers for Disease Control and Prevention on Tuesday issued an advisory to doctors and the public about the "increased risk of dengue virus (DENV) infections in the United States in 2024."

Dengue virus is a tropical disease spread by mosquitoes in tropical and subtropical areas of the world.

"Global incidence of dengue in 2024 has been the highest on record for this calendar year; many countries are reporting higher-than-usual dengue case numbers," the CDC said. 

"In 2024, countries in the Americas have reported a record-breaking number of dengue cases, exceeding the highest number ever recorded in a single year," the agency added.

As of June 24, more than 9.7 million dengue cases had been reported in the Americas, which is twice as many as what was reported in all of 2023 at 4.6 million cases.

In March, Puerto Rico declared an epidemic after a spike in dengue cases. Other dengue-endemic areas include the U.S. territories of American Samoa, and the U.S. Virgin Islands, and freely associated states, including the Federated States of Micronesia, the Republic of Marshall Islands, and the Republic of Palau.

What are symptoms of dengue fever?

About one in four people who are infected with dengue will get sick, according to the U.S. Centers for Disease Control and Prevention. Mild symptoms can include fever, nausea, vomiting, rash, and aches and pains and typically last anywhere from two to seven days. 

Most people will recover after about a week, the CDC says.

For about one in 20 people who get sick with dengue, it can develop into a severe case, according to the agency – including shock, internal bleeding, and even death. 

Infants and pregnant women are at higher risk of developing severe dengue.

Dengue fever prevention

The CDC says the best way to prevent dengue is by avoiding mosquito bites. A dengue vaccine is approved for use in some children who live in areas where dengue occurs frequently.

The vaccine, however, is not approved for use by U.S. travelers who are visiting but not living in an area where dengue is common.

Hotter temperatures accelerate dengue cases

Rising temperatures and rapid urbanization have accelerated the pace of infections worldwide.

Poor sanitation and a lack of robust health systems have contributed to a rise in cases, but experts say droughts and floods linked to climate change are causing greater transmission of the virus, with stored water and heavy rains attracting mosquitoes.

Dr. Gabriela Paz-Bailey, chief of the dengue branch for the CDC in Puerto Rico, previously noted that higher temperatures also are extending the mosquito’s habitat and helping the virus develop faster inside the mosquito, leading to higher viral loads and higher probability of transmission.

"These infections are a symptom of some big underlying trends happening in the world," Dr. Jeremy Farrar, chief scientist of the World Health Organization, said in December. "Climate change is seemingly so difficult to address, and so many countries are now becoming urbanized, I can see dengue and the other diseases…becoming increasingly frequent and increasingly complex to deal with."

The Associated Press contributed to this report. It was reported from Cincinnati.