Twenty-one Americans have been diagnosed with a virus that originated in sloths and is transmitted by mosquitoes.
The US Centers for Disease Control (CDC) said the patients were diagnosed with the Oropouche virus after returning to the United States from Cuba.
Twenty of the cases occurred in Florida and one in New York. The most common symptoms were fever, muscle aches, headaches, fatigue and stiffness.
Three patients were hospitalized, but there were no deaths.
The Oropouche virus is transmitted by mosquitoes in tropical areas of the Caribbean and South America, where it has caused an unprecedented outbreak since late last year.
The Oropouche virus is nicknamed sloth fever not because it is spread by sloths, but because animals can carry the disease.
The Oropouche virus is mainly transmitted through the bites of an insect called a mosquito. Sometimes mosquitoes also transmit it.
In rare cases, it can cause brain swelling and death, and claimed the lives of two healthy Brazilian women earlier this year.
In 2024, more than 8,000 cases have been reported in Central and South America, resulting in two deaths, one miscarriage and four newborns with birth defects.
Nineteen cases were reported in Europe earlier this month, prompting a warning from the European Centre for Disease Control.
The Oropouche virus is transmitted by mosquitoes and a small blood-sucking insect called a gnat.
Despite its nickname, sloth fever is not caused by contact with sloths.
Instead, it got the nickname because scientists believe sloths can carry and contract the disease. Experts suspect other animals, such as birds, can also transmit the virus.
If you are bitten by an insect carrying Oropouche, there are no medications to treat it and no vaccines to prevent it. The only defense against the disease is to completely avoid bites when traveling to these regions.
The 21 infected Americans ranged in age from 15 to 94, with an average age of 48. The most common symptom was fever (95 percent), followed by muscle aches (86 percent), headache (76 percent), fatigue (62 percent) and joint stiffness (57 percent).
Patients also reported diarrhea, abdominal pain, nausea, vomiting, rash, back pain, and bloody mucus.
Less than one in 20 people who contract the disease will develop more severe, life-threatening symptoms, such as severe bleeding, meningitis (inflammation of the membranes that protect the brain) and encephalitis (inflammation of the brain itself).
It can also cause birth defects and miscarriages.
It is unclear whether any of the patients included in the CDC report were pregnant. Information on pregnancy status was not collected for confidentiality reasons.
The agency recommended that doctors report possible Oropouche infections to state or local health authorities to expedite testing and prevent spread. Patients should avoid taking nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, to reduce the risk of bleeding.
To prevent infection, the CDC recommends wearing long sleeves and pants, using insect repellent, and staying in places that use screens on windows and doors.