Cases of mosquito-borne disease dengue fever rising in the Americas, CDC says

Dengue fever, the world’s most common mosquito-spread disease, is spiking in the Americas, with 2,241 cases detected in the U.S. between Jan. 1 and Monday, the Centers for Disease Control and Prevention said this week.

The rate of dengue fever infection in North, Central and South America has increased dramatically. There were over 4.6 million cases of the disease last year, and there have already been over 9.7 million cases between Jan. 1 and Monday, the CDC said.

There were 4,000 deaths in the region in 2023. CDC officials did not say how many, if any, patients have died of dengue so far in 2024.

In the U.S. and associated territories, Puerto Rico has the most cases thus far in 2024 at 1,498. It has declared a dengue fever public health emergency. Sporadic local transmission of dengue is also found in Florida, Hawaii and Texas, and has been observed in California and Arizona during the past two years, the CDC said.

Outbreaks are a year-round risk in the tropics of the world, happening every two to five years, according to a CDC travel notice. 

Since the disease is spread by mosquitoes, travelers or people who live in those climates should use bug spray, wear long-sleeved clothing outdoors, and sleep either in a room with air conditioning or a room with screened windows. Stagnant pools of water should be emptied and potted plants monitored to ensure mosquitoes are not laying eggs there.

Outside of Puerto Rico, other U.S. territories that have high rates of dengue infection include American Samoa, the U.S. Virgin Islands, the Federated States of Micronesia, the Republic of Marshall Islands and the Republic of Palau.

As of May 31, there had not been any dengue cases reported in Texas thus far in 2024. Hawaii has reported five travel-related cases as of Sunday.

In Florida, there have been 237 travel-related cases, and eight locally-spread cases, with three patients getting sick in January, one in February, two in March, and one each in April and June. Miami-Dade County has seen six cases reported, with one case reported each from Hillsborough and Pasco Counties.

Dengue fever is caused by four separate but related viruses, DENV-1, -2, -3 and -4. Around 25% of all DENV infections cause symptoms, which begin after an incubation period of five days to a week. These symptoms can last for three to 10 days, and include nausea, vomiting, rash, joint pain, bone pain, pain behind the eyes, headache or low white blood cell counts.

Specific clinical warning signs of a more serious infection can include abdominal pain or tenderness, persistent vomiting, accumulating too much fluid in the body, bleeding in the mouth, stomach, intestines or nose, lethargy or restlessness, a continued rise in the ratio of red cells to other cells in a patient’s blood and liver enlargement.