(BBC) A mysterious virus once confined to the Amazon is now spreading more widely around the Americas, after undergoing genetic changes that may make it more potent.
Until recently, Oropouche virus was a relatively-unknown disease largely confined to within the Amazon basin in South America. But since late-2023, the virus has been spreading beyond its usual range.
It has already caused more than 8,000 cases of the disease – often known by its nickname “sloth fever” – in five countries during the first seven months of 2024. The virus also recently caused the deaths of two women in Brazil and the potential deaths of two unborn children.
The rapid increase in cases of Oropouche, which is spread by biting insects, led the United States Centers for Disease Control and Prevention (CDC) to issue a health advisory alert to doctors in the US.
The first cases of the virus in Europe were detected in June and July 2024 in travellers who had been infected while visiting Brazil and Cuba.
How does the virus spread?
Oropouche is transmitted when a person or animal is bitten by insects carrying the virus. It is thought to be spread most commonly by the pinhead-sized midge species Culicoides paraensis, which are abundant across large parts of the Americas. But the virus may also be spread through bites by the Culex quinquefasciatus and Ochlerotatus serratus mosquitoes.
Direct human-to-human transmission of the virus has not been observed.
Once in the blood stream it can quickly spread around the body, and can cross the blood-brain barrier to get into the central nervous system. It appears to particularly accumulate within both the brain and liver.