‘Sloth fever’ update: Symptoms and what U.S. travelers need to know as the CDC issues a new Oropouche virus warning

The Centers for Disease Control and Prevention (CDC) has reported a surge in cases of “Sloth Fever,” or Oropouche virus infection, among U.S. residents linked to travel to Cuba. The Florida Department of Health has identified roughly 30 cases in Florida, WPTV reported, all associated with travel from Cuba, and an additional case has been reported in New York.

The Pan American Health Organization (PAHO) has also issued a warning about the virus’s spread to new regions, including parts of South America, such as Brazil, Bolivia, Peru, and Cuba. PAHO considers the risk to both North and South America to be high.

What we know about the virus

Oropouche virus, known for causing Sloth Fever, was previously confined to the Amazon basin in South America. However, since late 2023, the virus has expanded its reach, causing over 8,000 cases across five countries in the first seven months of 2024. This increase has resulted in two deaths in Brazil and possible deaths of two unborn children, raising significant concerns.

The virus is primarily transmitted by small biting flies and mosquitoes. It is found in animals such as howler monkeys, marmosets, and sloths (hence the nickname). Oropouche virus can cross the blood-brain barrier, accumulating in the brain and liver.

Until recently, the virus was relatively unknown outside the Amazon. Genetic changes may have increased its potency, allowing it to spread beyond its traditional range. This rapid expansion has led the CDC to issue a health advisory, especially after the first European cases were detected in June and July 2024 among travelers returning from Brazil and Cuba.

Symptoms to watch for

Symptoms of Sloth Fever typically appear within a week of exposure and include:

• Fever
• Muscle aches
• Headaches
• Fatigue
• Joint pain
• Gastrointestinal issues such as diarrhea and nausea

Of the recently discovered U.S. cases, the CDC reported that “Most patients had self-limited illness,” but added, “At least three patients experienced recurrent symptoms after resolution of the initial illness.”

Current situation and response

The CDC is working with state public health jurisdictions and international partners to enhance detection and surveillance of the virus. Their efforts include developing a rapid response plan, assisting with diagnostic testing, and updating travel advisories. Pregnant women are advised to avoid travel to affected regions due to the increased risk of complications.

State and local health departments are being encouraged to report cases to ArboNET, the national arboviral disease surveillance system.