Child collides with sloth while ziplining in Costa Rica
A child speeding through a rainforest on a zipline in La Fortuna, Costa Rica, on March 13, collided with a sloth clinging to the rope. (Go.Adventure Arenal Park via Storyful)
A potentially deadly virus called “sloth fever” has put health officials on alert after the number of cases rose significantly in the United States and Europe.
The Centers for Disease Control and Prevention (CDC) issued an important alert to its Health Alert Network after over 8,000 cases of oropouche virus (sloth fever) were reported between January 1 and August 1, 2024, with two deaths and five cases of transmission resulting in fetal death or congenital abnormalities.
In Florida, 20 travel-related cases of the virus have been reported, nine of them last week.
According to the CDC, the virus is primarily transmitted through the bite of infected midges, which are tiny biting insects. Mosquitoes can also transmit the virus.
Three-toed sloth, Amazon, Brazil, South America (Image credit: Hoberman Collection/Universal Images Group via Getty Images)
The disease is often referred to as “sloth fever” because transmission of the Oropouche virus typically occurs in forest areas between insects and non-human hosts such as sloths, birds and rodents.
Oropouche virus cases
Countries where cases have been reported include Brazil, Bolivia, Peru, Colombia and Cuba.
Travel-related cases have also been confirmed in the USA and Europe: the virus was detected in travellers returning from Cuba and Brazil.
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The CDC said reports of cases from other countries are expected.
What is the Oropouche virus?
According to the CDC, the Oropouche virus was first discovered in Trinidad and Tobago in 1955 and is endemic in the Amazon basin. Previous outbreaks have been described in Bolivia, Brazil, Colombia, Ecuador, French Guiana, Panama and Peru. In 2014, a child was infected in Haiti.
According to the CDC, the current outbreak is occurring in endemic areas and new areas outside the Amazon basin in 2024. Although travel-related cases have been identified in the United States, there is currently no evidence of local transmission within the United States or its territories.
Humans can become infected while staying in forested areas and are likely responsible for introducing the virus into urban environments.
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Although the greatest risk of disease is in people exposed to midges or mosquitoes infected with the virus, the risk factors for more severe disease from Oropouche virus are not well defined.
Earlier this year, two deaths in otherwise healthy, non-pregnant women and five cases in pregnant women with signs of vertical transmission of the virus to the fetus and associated fetal death or congenital abnormalities were reported in Brazil.
The CDC issued a warning about the possibility of transmission from mother to fetus during pregnancy.
Travelers to areas with transmission of Oropouche virus should take preventive measures to avoid contact with mosquitoes and midges during travel and for three weeks afterward or, in the case of infection, during the first week of illness to prevent further spread of the virus and possible introduction into unaffected areas in the United States.
Symptoms of the Lazy Fever Virus
According to the health authorities, about 60% of people infected with the Oropouche virus develop symptoms. The incubation period is usually 3-10 days.
The initial clinical presentation is similar to that caused by dengue, Zika and chikungunya viruses and features an acute onset of fever, chills, headache, myalgia and arthralgia.
Other symptoms may include eye pain, sensitivity to light, nausea, vomiting, diarrhea, fatigue, ash, conjunctivitis, and abdominal pain.
The first symptoms usually subside after a few days, but in a large proportion (about 70%) the symptoms may recur days to weeks after the initial illness has subsided.
Although the disease is generally mild, it is estimated that less than 5% of patients experience severe occipital pain, dizziness, confusion, lethargy, photophobia, nausea, vomiting, neck stiffness and nystagmus.
People at risk of more severe disease are likely to include those who can also become seriously ill from other vector-borne viral infections, such as people aged 65 or older or people with underlying medical conditions such as immunosuppression, high blood pressure, diabetes or cardiovascular disease.
There are currently no specific treatments or vaccines available against Oropouche virus disease.
Patients who develop more severe symptoms should be hospitalized for close observation and supportive care. Pregnant women with laboratory-confirmed oropouche virus infection should be monitored throughout pregnancy and live-born infants should be carefully examined, the CDC noted.
