No, you don’t get “sloth fever” from sloths, but you do get it from biting midges (also called “no-see-ums”) and certain mosquitoes. Oropouche virus, as it’s formally known, isn’t a new problem (it’s been around in parts of the world since 1955), but it recently became of particular concern in the U.S., where it had never been detected before. Since Oropouche is most common in South America and the Caribbean, doctors are warning that the spring break travel season could cause an uptick in cases of the insect-borne virus, which is especially worrisome for pregnant women since it can cause birth defects.
RELATED: CDC Warns Dengue Cases Are Rising in the U.S.—How to Protect Yourself.
What is Oropouche virus?
Oropouche is a viral infection that spreads through the bites of infected midges or certain mosquitoes. It’s called sloth fever because the insects can also spread it to specific primates, including sloths.
According to the World Health Organization (WHO), “The Oropouche virus is present mostly in South America and the Caribbean, but since December 2023 more cases were reported, totalling over 10,000 cases in 2024, including from areas in the region where it was not previously detected.”
“In 2024 concerns arose about possible complications of Oropouche virus infection including two deaths in previously healthy infected adults, and of possible negative outcomes of infection during pregnancy with associated fetal death, miscarriage, and microcephaly in newborns, that requires further investigation and research,” they state.
What are the symptoms of sloth fever?
The symptoms of sloth fever are similar to those of other insect-borne diseases like Zika, dengue, and chikungunya. Therefore, it is often misdiagnosed, the WHO notes.
Common symptoms are:
- Fever
- Headache
- Joint pain
- Body aches
- Chills
- Naseau and vomiting
- Rash
What is the risk of Oropouche in the U.S.?
California, Colorado, Wisconsin, Kentucky, New York, and New Jersey all reported one case, while Florida reported the remaining 103. Many of these people were infected last June, July, and August in Cuba, where the virus had newly emerged. Globally, Bolivia, Brazil, and Peru have been hotspots for the virus.
“Case numbers have been steadily increasing this year. In areas with previous Oropouche transmission the number of cases have approximately doubled compared to last year and there have been many reports of cases in new areas,” Stephen Vaughan, MD, an infectious disease specialist at the University of Calgary, told Salon. “Due to the nonspecific presentation and limitations in testing for this virus in most countries, the number of reported cases are an underestimate of the true burden of disease.”
“Climate change has allowed the expansion of mosquito vectors into new areas exposing more humans,” Vaughan continued. “Also, degradation of natural habitats have driven mosquitos into surrounding areas. Ease of travel (airplanes) and the relative lack of symptoms with Oropouche allow infected patients to carry the virus over long distances to new areas without detection, then expose a new population.”
How to stay safe from sloth fever:
Vaughan notes that the number of cases in the U.S. remains low, but spring travel to the Caribbean and South America could cause an uptick. And while research is still ongoing about Oropouche-related birth defects, he advises that pregnant travelers “discuss their travel itinerary with a travel health professional to determine their individualized risk.”
To protect from any insect-borne diseases, you can wear clothing that covers as much of your body as possible, use insect repellents, sleep with mosquito nets, install window screens, and stay in places with air conditioning.
There is no vaccine or antiviral medication for Oropouche. According to the CDC, treatment typically includes rest, fluids, and acetaminophen (Tylenol). Those who develop more serious symptoms may need to be hospitalized.
If you believe you’ve been exposed to Oropouche, seek immediate medical attention.
