What To Know About Dengue—And Why Cases Are Rising

Topline

Several rare cases of locally acquired dengue—a viral infection spread by mosquitoes—were reported in Florida this year, and as the U.S. continues to see record-breaking heat, experts warn climate change is to blame for an uptick in mosquito-borne illnesses.

Key Facts

The Florida Department of Health issued mosquito-borne illness alerts for Broward County and Miami-Dade County after several cases of locally acquired dengue were reported.

Some four cases of locally acquired dengue have been reported in Florida between July 30 and August 5, bringing the total number this year to 10, according to the Florida Department of Health.

Of those 10 cases, eight were reported in Miami-Dade County and two in Broward County.

Beyond the cases acquired locally, the state notes that 190 cases contracted in dengue-endemic countries were reported in Florida this year, with 112 cases contracted in Cuba alone.

Dengue is a viral infection spread through the bite of a female mosquito that causes severe flu-like symptoms or sometimes fatal complications, like severe bleeding or severe organ problems.

Though most people who contract the virus are either asymptomatic or show mild symptoms, if left untreated, the mortality rate of severe cases can be as high as 20%—access to care lowers this number to about 1%.

Big Number

1,012. That’s how many cases of locally acquired dengue were reported in the U.S. in 2023, according to the Centers for Disease Control and Prevention. This is the first time the U.S. has reported locally acquired cases in the thousands since 2013, when 9,933 cases were confirmed. There were 1,247 travel associated cases of dengue in 2022, the second highest number in 12 years after the 1,474 reported in 2019.

Key Background

There are four types of Dengue: DEN-1, DEN-2, DEN-3 and DEN-4. Though very similar, each type reacts differently with the antibodies in human blood serum. In 1970, only DEN-1 and DEN-2 were naturally present in the U.S., but by 2004, all four types began circulating. Once infected with one type of dengue, patients are protected against all four for up to three months. After that period, they are only protected against the subtype they contracted and susceptible to the other three. Researchers have found secondary dengue infection to be more severe than the first. About one in four people who contract the virus fall ill and usually get better within one to two weeks. Mild symptoms include nausea, vomiting, a severe headache, fever, muscle and joint pain, pain behind the eyes, a rash and swollen glands. Severe symptoms include blood in vomit or stool, fatigue or restlessness, severe abdominal pain, rapid breathing, bleeding gums or nose, persistent vomiting, feeling weak, pale or cold skin and constant thirst. There’s no specific medication for treating dengue—the focus is on treating symptoms. The best form of prevention is avoiding mosquito bites.

Tangent

As of July 27, over three million cases of dengue have been reported worldwide, according to the European Center for Disease Prevention and Control. Malaria—another mosquito-borne virus—cases also rose in parts of the U.S. earlier this summer. Four people in Florida and one in Texas were treated for locally acquired malaria. This is the first time in 20 years that locally acquired malaria has been reported in the U.S. The World Health Organization attributes the spike in mosquito-borne illnesses to climate change, urbanization and deforestation. Climate change causes an increase in temperature, humidity and precipitation, all conditions under which mosquitos thrive. According to the report, cases of dengue increased from a little over half a million globally in 2000 to 5.2 million in 2019. The Earth recorded its hottest July this year and the U.S. has witnessed deadly, record-breaking heat all summer.

Surprising Fact

Dengue is also known as breakbone fever due to severe joint pain and muscle spasms it causes, according to a study published in StatPearls.

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