'Sloth virus' reported in Europe for 1st time — but what is it?

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The Oropouche virus, which some media outlets are calling a "sloth virus," has been seen in European travelers returning home from the Americas.

A close-up of a midge
A biting fly called a midge is the main spreader of Oropouche virus to people. (Image credit: U.S. Centers for Disease Control and Prevention)

Oropouche virus disease, a Zika-like illness that spreads in the Americas, has been detected in Europe for the first time, affecting people in Spain, Italy and Germany.

Meanwhile, officials are investigating whether the germ may cause poor outcomes in pregnancy, similar to those associated with Zika virus.

Oropouche virus can cause symptoms similar to Zika, including sudden fever, muscle aches, light sensitivity, eye pain, vomiting and rash. In roughly 4% of cases, the virus can infect the nervous system, causing inflammation around the spinal cord and brain or within the brain itself. Nonetheless, most people recover within several days to a month.

That said, recently, Brazil reported a handful of cases that investigators suspect passed from mother to fetus during pregnancy. These infections were tentatively linked to poor outcomes, including pregnancy loss and microcephaly, which causes a baby's head to be much smaller than average.

However, due to limitations in the data, the link between poor pregnancy outcomes and Oropouche virus has not yet been confirmed. The U.S. CDC and the Pan American Health Organization are currently investigating the potential risk.

Oropouche virus was first detected in 1955 in Trinidad and Tobago, and it's since caused outbreaks in various countries in South America, Central America and the Caribbean. So far this year, outbreaks have been reported in Brazil, Bolivia, Colombia and Peru, and Cuba reported its first-ever known cases.

Direct spread of the virus from person to person has never been documented. Instead, people most often catch the disease from a midge species called Culicoides paraensis. In addition, a handful of mosquito species can carry and spread the virus to people.

The midges that spread the disease aren't found in Europe, and "to date, there has been a lack of evidence as to whether European midges or mosquitoes could transmit the virus," the ECDC noted in its risk assessment. This lack of evidence, combined with the fact that the virus doesn't spread between people, makes catching the disease locally in Europe very unlikely.

The risk of catching the disease abroad is "moderate," however, and the ECDC recommends that people traveling to places where Oropouche virus spreads take precautions. Safety measures include using insect repellent and wearing long-sleeved shirts and long pants when outside. Insecticide-treated bed nets should also be considered in rooms that are not adequately screened or air-conditioned. There is no vaccine for Oropouche virus.

Although the risks of catching Oropouche virus during pregnancy aren't yet clear, Zika virus — which does have clear risks if contracted during pregnancy — spreads in the same areas. Therefore, the same safety tips would apply for preventing both infections, according to the ECDC.

Some headlines have referred to Oropouche virus as "sloth virus" or "sloth fever." That's because the pale-throated sloth (Bradypus tridactylus) may be a key animal host for the virus, with insects passing it from sloths to humans and back.

However, the main animal hosts of the Oropouche virus haven't yet been confirmed. A few contenders besides sloths include various wild birds and a few primates, such as capuchin (Cebus) and howler (Alouatta) monkeys.

This article is for informational purposes only and is not meant to offer medical advice.

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Nicoletta Lanese
Nicoletta Lanese
Channel Editor, Health

Nicoletta Lanese is the health channel editor at Live Science and was previously a news editor and staff writer at the site. She holds a graduate certificate in science communication from UC Santa Cruz and degrees in neuroscience and dance from the University of Florida. Her work has appeared in The Scientist, Science News, the Mercury News, Mongabay and Stanford Medicine Magazine, among other outlets. Based in NYC, she also remains heavily involved in dance and performs in local choreographers' work.