The Malburg virus, which is in the ebole family. These are marked by severe bleeding (haemorrhage), organ failure and, in many cases, death. These viruses are native to Africa, where sporadic outbreaks have occurred for decades. As noted above, Malburg recently flared up in Guinea in Africa.
It has a case fatality rate (CFR) or death rate of 90%. This means 9 in every 10 infected die. When one has the disease the internal organs essentially liquify and the patients dies.
Another ebola-like virus was recently found in the UK.
They have recently reported 2 suspected cases of the Malburg virus in Ghana. This is largely based on the viral haemorrhagic fever, but Malburg is suspected.
As the virus kills most of its victims it is unlikely to spread far because it kills most of its hosts.
The incubation period (interval from infection to onset of symptoms) varies from 2 to 21 days. Illness caused by Marburg virus begins abruptly, with high fever, severe headache and severe malaise. I do not believe the virus is contagious in the incubation period, but if may be easy to infect others when one becomes ill through fluid exchange, contaminated bedding, clothing, needles etc.
So I do not believe the Malburg virus will be of much threat to humanity because
one is generally not infectious in the incubation period, and it’s CFR is too high so it kills most of its hosts. Quarantine of individuals in close contact should work. The same is also true of the monkeypox virus although its initial rapid growth did suggest that it was airborne.