Brazil, which has recently suffered serious outbreaks of Zika virus and yellow fever, now faces a new threat, according to reports from local scientists: Oropouche fever.
The Oropouche virus, named for a river in Trinidad, where it was first isolated in 1955, circulates in monkeys and sloths in the Amazon jungle. The virus has caused occasional outbreaks, short but intense, in towns in tropical areas of Brazil, Peru and Panama, and on some Caribbean islands.
But in the last few years, Oropouche cases have turned up more often in urban areas, including some in northeast Brazil, where Zika began its explosive spread in this hemisphere.
Oropouche causes symptoms resembling those of dengue: high fever, headaches and joint pain, nausea and malaise. The infection is not normally fatal, although it can cause meningitis — dangerous brain stem swelling — if it reaches the spinal fluid. There is no vaccine.
The virus is typically transmitted by a biting midge, Culicoides paraensis, that ranges from Argentina to as far north as Wisconsin. The insects are known variously as no-see-ums, because of their size, or gunpowder midges, because they resemble black gunpowder grains.