In August 2024, the Centers for Disease Control and Prevention (CDC) issued a health advisory about emerging cases of Oropouche virus disease, or “sloth fever.” According to the bulletin, the disease had been identified in the United States and Europe in travelers returning from Cuba and Brazil.
Here’s what to know about this potentially dangerous illness.
What Is Sloth Fever?
Sloth fever, or Oropouche virus disease, is an illness that can develop in people infected with the Oropouche virus.
The Oropouche virus spreads primarily through the bites of biting midges and some species of mosquitoes. Biting midges are a type of small fly that feeds on blood; they are smaller than mosquitoes.
The virus is most often found in the Amazon basin. Previous outbreaks have taken place in locations like Bolivia, Brazil, and Colombia.
People traveling in forested areas are most likely to be infected. They may later introduce the virus to populated regions as the insects hitch a ride back to urban areas.
In 2024, more than 8,000 infections have been reported throughout South America and Central America.
As of Aug. 16, 2024, the CDC said 21 cases had been identified in Florida and New York. All cases involved travelers returning from Cuba. There is no evidence of local transmission of sloth fever within the United States at this time.
How Does the Oropouche Virus Spread?
Sloth fever typically spreads to humans when an infected biting midge or mosquito bites them.
Health officials in Brazil are also investigating reports of pregnant women passing the Oropouche virus to their unborn babies.
Sloth Fever Symptoms
About 60% of people infected with the Oropouche virus experience symptoms, according to the CDC.
The illness’ incubation period is typically up to 10 days.
Symptoms of Oropouche often mirror those of dengue and Zika viruses, including:
- Chills
- Fever
- Headache
- Muscle aches
- Nausea
- Stiff joints
- Vomiting
Other symptoms may include:
- Abdominal pain
- Diarrhea
- Eye pain
- Fatigue
- Light sensitivity
- Rash
Symptoms can recur, but they are typically mild. In rare cases, people exposed to the virus may develop serious bleeding conditions or neuroinvasive disease. This happens in under 5% of cases.
Vulnerable populations, such as people with underlying medical conditions or pregnant people, are at greater risk for more severe symptoms.
Is Sloth Fever Deadly?
Death from Oropouche is rare but possible.
The virus can lead to serious diseases like meningitis, encephalitis, and bleeding conditions in certain cases.
How is Sloth Fever Treated?
According to the CDC, there is no specific antiviral treatment or vaccine available for Oropouche at this time. However, most people recover in less than a month.
Treatment for symptoms can include rest, fluids, painkillers, and antipyretics that reduce fever. Acetaminophen, such as Tylenol, is the preferred treatment for Oropouche-related fever and pain.
Aspirin and other non-steroidal anti-inflammatory drugs should not be used to reduce the risk of hemorrhage.
It’s important to continue to prevent insect bites during illness to avoid further spread, especially in areas where mosquitoes or biting midges are active.
People who develop more severe symptoms should be hospitalized for close observation and comprehensive treatment.
Preventing Sloth Fever: Tips for Travelers
The CDC offers guidance for travelers to protect themselves from sloth fever and other viruses transmitted by insects.
- Use a U.S. Environmental Protection Agency-registered insect repellent and wear long-sleeved shirts and pants to prevent insect bites when in forested areas and other outdoor locations.
- Mosquitoes and other biting insects are often most active during dawn and dusk. If possible, limit outdoor activities during these times.
- If you’re camping or staying in an area with a lot of mosquitoes, use a mosquito net over your sleeping area. Stay clear of standing water that attracts insects.
- Know the signs: Be aware that the most common symptoms of Oropouche virus are fever and headache. Symptoms usually begin up to 10 days after being bitten by an infected midge or mosquito. Most people infected with the virus feel better within a week, but symptoms may return.
- Travelers who have been in areas with Oropouche virus transmission should prevent insect bites for at least three weeks after travel.
- Pregnant travelers should discuss steps to prevent insect bites and potential risks with their health care provider. The CDC recommends reconsidering nonessential travel if you’re pregnant and plan to travel to countries with an Oropouche virus outbreak. If travel is unavoidable, pregnant travelers should strictly follow Oropouche virus prevention recommendations to stay safe.
If You Think You Have Oropouche Virus
You should seek medical care if you traveled to an area with Oropouche transmission and develop fever, chills, headache, joint pain, or muscle pain during your travel or within two weeks after your trip. Tell your health care provider when and where you traveled.
If you think you’ve been exposed to Oropouche virus, you can also contact your state or local health department for more information and to ask for testing.
For current testing and case reporting guidance, visit the CDC’s website.
Sources
U.S. Centers for Disease Control and Prevention, Increased Oropouche Virus Activity and Associated Risk to Travelers. Link.