The WHO said there were currently nine deaths and 16 suspected cases with symptoms including fever, fatigue, diarrhea and vomiting. The agency said it was sending medical experts to help officials in Equatorial Guinea stop the outbreak and was also sending protective equipment for hundreds of workers.
Like Ebola, the Marburg virus originates in bats and spreads between people via close contact with the bodily fluids of infected people, or surfaces, like contaminated bed sheets. Without treatment, Marburg can be fatal in up to 88% of people.
The rare virus was first identified in 1967 after it caused simultaneous outbreaks of disease in laboratories in Marburg, Germany and Belgrade, Serbia. Seven people died who were exposed to the virus while conducting research on monkeys.
There are no authorized vaccines or drugs to treat Marburg, but rehydration treatment to alleviate symptoms can improve the chances of survival.
In a 2004 outbreak in Angola, Marburg killed 90% of 252 people infected. Last year, there were two reported Marburg deaths in Ghana.