Oropouche virus is an arthropod-borne virus – meaning it’s transmitted to humans if they’re bitten by infected midges or mosquitoes. It’s the most prevalent arthropod-borne viral disease in south America – after dengue virus.

The virus was first discovered in 1955 in a forest worker who had contracted it working near the Oropouche river in Trinidad and Tobago. The first large outbreak was reported in the 1960s in Belém, Brazil, where 11,000 cases were recorded.