A new outbreak of the deadly Marburg virus has infected a suspected 25 people and potentially killed nine in the Central African country of Equatorial Guinea, the World Health Organization announced this week. There have been 15 previously confirmed Marburg outbreaks, according to data from the Centers for Disease Control and Prevention. But the current one, with a beginning that dates back to early January, is Equatorial Guinea’s first.
Following the WHO’s official confirmation of the outbreak on Monday, neighboring Cameroon also reported two of its own suspected cases.
What Is the Marburg Virus?
The disease is in the same filovirus family as the more widely known Ebola virus. And similar to Ebola, Marburg is a rare but often deadly hemorrhagic fever. It has a case-fatality rate between 23% and 90%, depending on the outbreak, with an average fatality rate of 50%.
Marburg was first documented passing to people from African green monkeys transported to European laboratories in 1967. The virus’s reservoir host is African fruit bats, which don’t show apparent signs of infection but can pass the disease onto humans and non-human primates, according to the CDC.
Between people, the virus is spread by contact with bodily fluids (including semen) or contaminated objects like bedding, clothes, and medical equipment.
Once infected, symptoms start suddenly after an incubation period of between two and 21 days. Illness begins with fever, chills, headache, and muscle aches. Then, a rash often develops, followed by nausea, vomiting, chest pain, a sore throat, abdominal pain, and diarrhea. These symptoms often become increasingly severe and can lead to system-wide problems like organ inflammation and failure, internal bleeding, significant weight loss, jaundice, and ultimately death.
There are no currently approved anti-viral treatments or vaccines for Marburg (unlike for Ebola), but supportive care like IV fluids and treating symptoms can greatly boost survival.
What’s Happened in Past Outbreaks?
The largest ever Marburg virus outbreak led to 252 documented cases and 227 deaths in Angola from 2004-2005. The second largest outbreak killed a known 128 people and infected 154 in the Democratic Republic of Congo from 1998-2000.
However, unlike Ebola, all other confirmed Marburg outbreaks have been much smaller—usually only causing a handful of infections. Marburg is slightly less contagious than its viral cousin, and these past outbreaks have been managed and resolved through quarantine and containment efforts.
Prior to the ongoing situation, the most recent known outbreak occurred in Ghana between June and September 2022. Three cases, all within the same household, were recorded, and two of the three people died.
So far, the current outbreak would be the fourth largest, if all infections are confirmed. The WHO reported that it has sent samples from the deceased to the Pasteur Institute in Senegal for further analysis and is awaiting results.
How Are Health Authorities Responding Now?
In addition to collecting and testing samples, the WHO noted that contact tracing and medical teams have been deployed to Equatorial Guinea. The international agency said it also has epidemiologists, infectious disease prevention experts, and others on the case. The UN organization is further “facilitating the shipment” of lab equipment and personal protective gear.
Further, multiple experimental Marburg vaccines are in development, all of which have shown promising results in monkey studies. Researchers are interested in testing these vaccines amid the current outbreak, according to a news report from Nature. However, a successful vaccine trial is unlikely to happen because a quick and effective quarantine response could end the outbreak before vaccines could even be administered, WHO officials and scientists reportedly noted in a Tuesday meeting.
“I cannot emphasize enough the need for speed,” said John Edmunds, a University of London epidemiologist, at the WHO meeting, according to Nature. “It’s a double-edged sword, isn’t it? It’s good news for public health and the people of Equatorial Guinea, but perhaps bad news for science.”
If the WHO does opt to approve a human vaccine trial in the current outbreak, the agency will decide which of the five candidate vaccines to test. Even if this particular outbreak doesn’t offer enough opportunity for a full test of vaccine efficacy, it’s possible that a partial trial could still provide useful data.