The U.S. Centers for Disease Control and Prevention will issue its second-highest level of travel notice for Rwanda, recommending people to avoid nonessential travel due to the Marburg disease outbreak in the east African country,

Marburg virus is named after the town in Germany where it first emerged. In 1967, there were simultaneous outbreaks at laboratories in Marburg and Belgrade in Serbia (then part of Yugoslavia). The outbreak was caused by African green monkeys imported from Uganda for use in experiments. Seven people died.

Marburg has caused small, episodic outbreaks since first being identified, most recently last year in Tanzania and Ghana. It is one of the deadliest known viruses, with no approved vaccines or specific treatments.