GAINESVILLE, fla. – In 2024, “sloth fever” hit the news cycle as a new public health threat: The virus was found in people who’d recently traveled to Cuba, and the serious health risks associated with the disease prompted concern about whether it could spread and become established in the U.S.
Sloth fever is the popularized name of the illness caused by the Oropouche virus, which is endemic to countries like Brazil, Bolivia, Colombia, Cuba and Peru, and it is indeed primarily spread from person to person by a species of no-see-um. In 2024, about 105 travel-related cases of Oropouche virus infection were spotted in the U.S. – about 103 of which arrived in Florida, according to the U.S. Centers for Disease Control and Prevention. The infected people had recently traveled to Cuba. Because the species of no-see-um that transmits Oropouche virus had never been found in Cuba, researchers suspected that mosquitoes were transmitting the virus from person to person. If so, the virus would be much more likely to establish in Florida and elsewhere in the U.S.
Sorting mosquitos after they’d drank blood with oropouche virus. Photo: Courtesy UF/IFAS FMEL
In general, the Oropouche virus causes fever, chills, headache, muscle and joint aches and a bumpy rash. But the biggest concern is it could cause fetal birth defects,both cognitive and developmental,if a pregnant woman is infected – harkening back to concerns like that of the Zika outbreak in 2016-2017.
But researchers have good news: The main two types of disease-spreading mosquitoes in the Southeastern U.S. are incredibly bad at spreading the Oropouche virus, so even if travel cases arrive, and that person is bitten by a mosquito, it is unlikely the virus will spread to the next person bitten, said Barry Alto, associate professor at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS). The research is the result of a grant from the CDC and was published last week in the peer-reviewed journal PLOS Neglected Tropica
Low Risk of Local transmission of Oropouche Virus in Florida, UF/IFAS Research Finds
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Recent research from the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) suggests a low likelihood of the Oropouche virus becoming established and locally transmitted in Florida. A study involving over 2,000 mosquitoes revealed that very few were infected with the virus, and even fewer carried it in their saliva – meaning they were unable to spread it through bites.
Oropouche Virus and Recent Florida Cases
The oropouche virus is a mosquito-borne illness typically found in Central and South America. In 2023, Florida health officials confirmed several locally acquired cases in Florida, raising concerns about potential spread. The virus causes symptoms similar to dengue fever and chikungunya, including fever, headache, muscle pain, and rash.
UF/IFAS Research Findings
researchers at the UF/IFAS florida Medical Entomology Laboratory (FMEL) conducted a complete study to assess the potential for local transmission. the study focused on aedes mosquitoes, known vectors of other arboviruses like dengue and Zika.
“We tested over 2,000 mosquitoes to identify how well each of them spread the Oropouche virus,” explained Nathan Burkett-Cadena, an associate professor at UF/IFAS FMEL. “We found that few had the infection inside them at all, and even fewer had the virus in their saliva, so they would be unable to spread the virus to the next person they bit.”
Burkett-Cadena stated,”We feel it’s very unlikely the virus will become established and transmitted locally.”
Future Research Directions
While the risk appears low for Aedes mosquito transmission,researchers are continuing to investigate other potential vectors. Future studies will focus on:
* Biting Midges (No-See-Ums): Determining if these insects, also known as biting midges, can carry and transmit the Oropouche virus.
* Vertical Transmission: Investigating whether mosquitoes can transmit the virus to their offspring (vertical transmission).
About UF/IFAS
The University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) is dedicated to developing and disseminating knowledge in agriculture, human, and natural resources. With a network of research facilities, county Extension offices, and a distinguished faculty and student body, UF/IFAS provides science-based solutions to benefit florida’s industries and residents. Learn more about UF/IFAS.
– Lourdes Mederos, UF/IFAS
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