‘Sloth fever,’ or the Oropouche virus, has entered the US, here’s what to know

A disease transmitted by mosquitoes — the Oropouche virus, also known as sloth fever — has been detected in the United States.

Travelers returning to the U.S. from Cuba contracted the virus in recent months, as reported by The Associated Press. No fatalities have been reported.

The Oropouche virus is endemic in the Amazon basin and has also been reported in South America and the Caribbean.

More than 8,000 cases were reported globally between Jan. 1 and Aug. 1, 2024, including two deaths and five cases of transmission from mother to fetus, the CDC noted in an Aug. 16 advisory.

Sloth fever has been reported in Brazil, Bolivia, Peru, Colombia and Cuba. 

So far, 11 cases have been identified in travelers returning from Cuba and Brazil, the CDC stated.

“Although travel-associated cases have been identified in the United States, no evidence of local transmission currently exists within the United States or its territories,” the agency said.

“As testing and surveillance for Oropouche virus disease increase in the Americas, reports of cases from additional countries are expected.”

What is the Oropouche virus?

The Oropouche virus first emerged in Trinidad and Tobago in 1955. 

Since then, it has had “limited circulation” in regions of South America, particularly in forested areas, according to the CDC.

The disease is typically spread through bites from mosquitoes and midges (small flies, particularly the Culicoides paraensis species).

Three-toed sloths and birds have been identified as “natural reservoirs” for Oropouche, which means they act as hosts of the disease.

“The virus doesn’t spread from person to person,” Dr. Marc Siegel, senior medical analyst for Fox News and clinical professor of medicine at NYU Langone Medical Center, confirmed to Fox News Digital.

“There is some risk to the fetus in terms of birth defects.”

Symptoms of Oropouche

Oropouche, classified as an arbovirus, is often mistaken for other similar viruses, like Zika, dengue, chikungunya and malaria, according to the CDC.

Symptoms of the virus include fever, headache, muscle aches, stiff joints and chills.

Some may develop a rash that begins on the torso and spreads to other body parts.

Symptoms usually begin within four to eight days of being bitten, and last for three to six days.

“Symptoms can abate and reoccur,” Siegel noted.

In severe cases, patients may develop meningitis, encephalitis or other “neuroinvasive” diseases, the CDC stated.

For those patients, symptoms can include intense headaches, dizziness, confusion, nausea, vomiting, light sensitivity, lethargy, stiff neck and involuntary eye movements. 

“Around 4% of patients develop [neurologic symptoms] after the first febrile illness,” Siegel said.

Treatment and prevention

Most people who contract Oropouche will recover on their own without any long-term effects, the CDC stated.

“There are no vaccines for prevention and no treatments,” Siegel said.

The best means of prevention is to avoid bites from midges and mosquitoes, according to experts.

“People are advised to take preventive measures, including the use of repellents, clothing that covers legs and arms, and fine mesh mosquito nets, and to take extra precautions during outbreaks, particularly for vulnerable groups such as pregnant women,” the Pan American Health Organization advised in an alert.