Marburg Virus

Marburg is an enveloped single-stranded RNA filovirus, that belongs to the same family as Ebola viruses and causes severe hemorrhagic fever. Marburg virus is named after the city of Marburg in Germany. Approximately 600 infected green monkeys (Chlorocebus aethiops) were shipped to Marburg, Frankfurt, and Belgrade in 1967. Laboratory workers in Marburg and Frankfurt apparently became infected after working with kidney cell cultures derived from infected monkeys. In Belgrade, a veterinarian became infected while performing an autopsy on a deceased monkey. Altogether, 32 people became infected and 7 died.

Marburg virus has a broad distribution range throughout Sub-Saharan Africa. The likely primary natural reservoir is the Egyptian fruit bat (Rousettus aegyptiacus) that lives in caves. Fruit bats harboring the virus do not exhibit any obvious signs of illness. 

Marburg virus can spill over from bats to old world monkeys, non-human primates (chimpanzees and gorillas) and humans. It is not known how Marburg virus spreads from bats to people but contact with bat feces or aerosols is most likely. Marburg virus spreads among people through contact with the blood or body fluids of infected patients. 

Approximately 20 outbreaks of Marburg virus have been recorded since 1975. Most Marburg outbreaks have been small, but a large outbreak occurred in Angola in 2004 to 2005 that resulted in 374 cases and 329 deaths (case fatality rate of 88%). 

In 2023, two outbreaks occurred in Equatorial Guinea and Tanzania, which are located on opposite sides of the African continent. On February 13, the Government of Equatorial Guinea declared a Marburg disease outbreak. There were 16 confirmed cases, of which 12 were fatal. An additional 23 probable cases were also reported, all of whom died. The WHO declared the outbreak over on June 8, 2023.

On March 21, 2023, Tanzania’s government declared the country’s first outbreak of Marburg disease. There were 8 confirmed cases, of which 5 died. These outbreaks occurred in the Kagera region of Tanzania, which is a transit hub and borders Burundi, Rwanda, and Uganda. 

In September 2024, Rwanda’s health ministry reported the country’s first Marburg virus outbreak. By the end of October, 66 people had become ill and 15 of them had died. Most of the patients were healthcare professionals who worked in two hospitals in the capital city, Kigali. More than 500 doses of Sabin Vaccine Institute’s experimental Marburg vaccine had been administered. On December 20, 2024, Rwanda declared the outbreak had ended. 

A medical student who had contact with a patient who was diagnosed with Marburg disease in Rwanda and his girlfriend developed flu-like symptoms upon their return to Germany. They had arrived by plane from Rwanda and then developed flu-like symptoms on a train from Frankfurt to Hamburg. Approximately 200 passengers were on the train. Officials cleared two tracks in Hamburg Central Station and evacuated the area. The two people were taken to University Hospital Eppendorf in Hamburg where they later tested negative for Marburg virus. 

On October 8, 2024, the US CDC issued a level 3 travel notice for Rwanda. A level 3 alert urges people to reconsider nonessential travel. The agency also announced it would begin screening travelers who have recently visited Rwanda. Traveler screening will begin on October 14 and apply to people who have been in Rwanda in the past 21 days. Passengers who have been in Rwanda will be rerouted to one of three international airports (Chicago’s O’Hare, New York City’s John F. Kennedy , and Washington, DC Dulles).

On January 20, 2025, Tanzania confirmed its second Marburg virus outbreak. There have been 2 confirmed and 31 suspected cases. Ten patients had died so far. The outbreak was concentrated in the Biharamulo district, which is a transit hub near international borders. This locale raised concerns about possible regional spread.

Following an incubation period of 2 to 21 days, patients infected with Marburg virus suddenly develop fever, chills, headache, and myalgia. A maculopapular rash may appear around the fifth day after symptom onset. Patients also may develop nausea, vomiting, diarrhea, abdominal pain, and sore throat. As the disease progresses, patients develop pancreatitis, liver failure, and massive hemorrhaging. Eventually, they suffer multi-organ failure. The case fatality rate has ranged from 23 to 90%. 

Unlike Ebola, there are no specific antiviral drugs for Marburg virus disease. The Sabin Vaccine Institute has developed an experimental Marburg vaccine and sent 2700 doses to Rwanda. The vaccine was being given to at-risk populations, including healthcare workers. 

Clinical diagnosis of Marburg virus disease is difficult because the signs and symptoms resemble other infectious diseases such as malaria, typhoid fever, dengue fever, Lassa fever or Ebola. The diagnosis can be confirmed by laboratory testing. Antigen-capture enzyme-linked immunosorbent assay (ELISA) testing, polymerase chain reaction (PCR), and IgM-capture ELISA can be used to confirm a case of Marburg virus disease within a few days of symptom onset. IgG-capture ELISA is useful to confirm infections later in the course of disease or after recovery. Virus isolation is possible but should only be done in a high containment laboratory with good laboratory practices. 

References

Schnirring L. Equatorial Guinea confirms its first Marburg fever outbreak. CIDRAP, February 13, 2023.

Centers for Disease Control and Prevention, Marburg Virus Disease, https://www.cdc.gov/vhf/marburg/index.html

Professor Francois Balloux, A few facts about Marburg virus, Twitter, March 26, 2023. 

Schnirring L. Rwanda reports first Marburg virus outbreak. CIDRAP, September 30, 2024.

Schnirring L. Tanzania confirms second Marburg virus case, CIDRAP, January 23, 2025.