The news that a man has died from Marburg virus in the West African nation of Guinea has raised fears of a larger outbreak of the infectious illness.
Sometimes involving bleeding from the ears and eyes, the disease has emerged several times over the past half century or so.
It can kill about nine in 10 of those infected.
There have been 12 major Marburg outbreaks since it was first discovered in 1967 in Germany, mostly in southern and eastern Africa.
Here we look at Marburg disease, where it comes from, how it spreads and what is being done to contain the latest outbreak:
What happened in the latest outbreak?
This is the first West African case of Marburg, which results from infection by a virus related to the one that causes Ebola, an outbreak of which starting in the same area and killed thousands between 2014 and 2016.
The Marburg patient died at the beginning of this month, but the cause was identified only by postmortem lab tests and details were passed on to the World Health Organisation late last week.
Intensive contact-tracing has been carried out to prevent further spread, with officials getting in touch with more than 140 people who may have been exposed to the virus.
What is Marburg virus disease?
This disease is named after the German town where, along with Frankfurt and Belgrade, it was identified in 1967 after spreading from laboratory monkeys imported from Uganda.
Other outbreaks have happened in Uganda, Angola, the Democratic Republic of Congo, Kenya and South Africa.
Cases have also been reported in the US and Netherlands, although these were traced back to Uganda.
The virus originates in fruit bats, which do not fall ill but pass the pathogen to people, directly or through other species such as monkeys or, possibly, pigs.
It spreads between humans when blood or other bodily fluids from an infected person come into contact with the broken skin or mucous membranes (such as those in the mouth, nose or eyes) of another person.
The WHO reports that the disease can also be caught from contaminated surfaces or materials, such as clothing or bedding.
No drugs or treatment
It takes between two days and three weeks for the disease to emerge after exposure to the virus.
Symptoms include fever, headaches, muscle aches and pains, diarrhoea and vomiting.
Patients may have what is described as a “ghostlike” appearance as the disease progresses, the WHO said.
Severe bleeding may develop in the gums and nose, along with areas where blood samples have been taken or intravenous drips inserted.
Fever continues and the patient may become aggressive or confused.
Death may result a little more than a week after symptoms show.
In the largest outbreak, in 2005 in Angola, 329 of the 374 cases proved fatal – a rate of 88 per cent.
While no medicine works against the Marburg virus specifically (although drugs and immune therapies are being developed), treatment of symptoms and rehydration improve survival.
What happens now?
No outbreak since the one in 2005 has caused more than a handful of deaths, so officials hope to contain this latest emergence.
A WHO team that was in Guinea to assist with an Ebola outbreak, which ended in June, will remain in the country to help authorities deal with the Marburg outbreak.
Along with contact-tracing, Guinea’s Ministry of Health and international partners have introduced various measures to contain the disease.
There is “active searching” for possible cases, health workers are being briefed, the public is being informed of the risks and a surveillance team is working in the village where the case occurred and in near by areas.
While there is a high risk of the disease causing further cases nationally, the WHO said, the chances of global outbreak are low.