The Marburg virus, which causes a severe disease that is in the same virus family that causes Ebola, has been identified in southwest Guinea near the borders of Sierra Leone and Liberia, according to the World Health Organization.
There has been one known death and 155 people are in mandatory quarantine, The Washington Post reported.
The region also faced a deadly Ebola outbreak this year that ended in June, according to the WHO statement.
It can be hard to tell the difference between Marburg and other tropical diseases, like malaria, because symptoms are similar, according to the statement.
Death rates range between 24% and 88%, depending on things like the type of care an infected person receives, the WHO says.
The organization says a man began having symptoms in late July and sought treatment. He tested negative for malaria.
He died Aug. 2, and the WHO and authorities investigated. Test results from an oral swab came back positive for Marburg and negative for Ebola. Test results were confirmed multiple times.
The Ministry of Health, CDC, WHO, and others are working to prevent further spread of the virus through efforts like contact tracing and watching for cases in health care facilities and communities.
Other disease outbreaks have caused problems in Guinea due to the country's shaky health care system.
But the WHO said experience in handling other mass outbreaks, including COVID-19, helped in the quick response to control the spread of the Marburg virus.
"We applaud the alertness and the quick investigative action by Guinea's health workers. The potential for the Marburg virus to spread far and wide means we need to stop it in its tracks," tweeted Matshidiso Moeti, MD, regional director for Africa at the World Health Organization.
The WHO calls the disease "epidemic-prone," meaning that it can spread easily between people if not prevented. There have been previous Marburg outbreaks in other parts of Africa, including Angola, Uganda, and South Africa.
But, the WHO says there is a low chance of global spread of Marburg. Health officials in neighboring countries are actively looking for cases.
News release, World Health Organization.
World Health Organization: "Marburg virus disease," "West Africa's first-ever case of Marburg virus disease confirmed in Guinea."
CDC: "Marburg hemorrhagic fever (Marburg HF)."
The Washington Post: "Guinea orders 155 people into quarantine after West Africa's first case of Marburg virus is detected."
The New York Times: "Guinea Declares Ebola Outbreak With at Least 3 Deaths."