(Bloomberg) -- Marburg virus had killed 12 people in Rwanda as of early October, touching off the nation’s first confirmed outbreak of the highly virulent disease that can have a fatality rate of close to 90%. From the same family as the Ebola virus, Marburg caused occasional outbreaks and sporadic cases mostly in Central and Southern Africa until Guinea, in West Africa, confirmed a single, deadly case in August 2021. Then in the following years, it popped up for the first time in other countries on the continent. The latest cases show once again how a pathogen found in fruit bats can cross the species barrier to infect humans, and raise the risk of a wider outbreak.
What is Marburg virus?
It’s a member of the Filoviridae family of viruses that can cause severe and potentially fatal hemorrhagic fever in people. Marburg virus disease was recognized in 1967, when outbreaks occurred simultaneously in laboratories in Marburg and Frankfurt, both in Germany, and in the Serbian capital, Belgrade. Cases were traced to green monkeys imported from Uganda for research and polio vaccine production. Nine years later, a closely related virus was found to have sparked a deadly outbreak in a village near the Ebola River in Congo, giving that disease its name. Since then, many more viruses known to cause similar illnesses in humans have been discovered around the world, with globalization, international travel and climate change aiding their spread.
What symptoms does it cause?
After an incubation period of two to 21 days, symptoms begin with a high fever, severe headache and severe malaise, often accompanied by muscle aches and pains. Watery diarrhea, abdominal pain and cramping, nausea and vomiting can begin on the third day. Diarrhea can persist for a week. The appearance of infected people at this phase has been described as showing “ghost-like,” drawn features, deep-set eyes, expressionless faces and extreme lethargy. Many develop severe bleeding, or hemorrhaging, at the end of the first week of symptoms. Fresh blood in vomit and feces is often accompanied by bleeding from the nose and gums. Spontaneous bleeding at sites where intravenous access is obtained to give fluids or obtain blood samples can be particularly troublesome. During the severe phase of illness, patients have sustained high fevers. Involvement of the central nervous system can result in confusion, irritability and aggression. Males occasionally experience inflammation of one or both testicles in the third week of the disease. In fatal cases, death occurs most often eight to nine days after symptom onset, usually preceded by severe blood loss and shock.
How is it diagnosed?
Without diagnostic lab tests, it can be difficult to distinguish Marburg virus from malaria, typhoid fever, shigellosis and meningitis or Ebola, Lassa fever and other viral hemorrhagic diseases. Samples collected from patients are an extreme biohazard risk. The World Health Organization recommends conducting tests under maximum biological containment conditions with specimens transported using a triple packaging system.
How do outbreaks start?
The African fruit bat Rousettus aegyptiacus is considered the reservoir host, or main carrier, of Marburg virus. Human cases have resulted from prolonged exposure to mines or caves inhabited by colonies of the flying mammals. Primates, such as monkeys and apes, can also be infected. Encroachment into forested areas and direct interaction with wildlife, such as “bush meat” consumption, facilitate the spread of Marburg and other filoviruses from animals to humans. Once a person is infected, the pathogen can be transmitted from person to person via direct contact through broken skin or mucous membranes with the blood, secretions, organs or other bodily fluids of infected people, and with surfaces and materials, such as bedding and clothing, contaminated with these fluids.
Who’s at risk?
Historically, people at highest risk include family members and hospital staff who care for patients infected with Marburg virus and haven’t properly used personal protective equipment or other infection-prevention measures. In the outbreak in Rwanda, a large percentage of the confirmed cases were health-care workers from two different health facilities. Veterinarians and laboratory or quarantine facility workers who handle non-human primates from Africa may also be at increased risk of exposure. Burial ceremonies that involve direct contact with the corpse of a person who had Marburg can also contribute to its spread.
Are there treatments and vaccines?
There is no approved cure for Marburg virus disease, although several approaches, including blood products, immune therapies, monoclonal antibodies and antivirals, are being evaluated, according to the WHO. Supportive care, especially rehydration with oral or intravenous fluids, and treatment of specific symptoms improves chances of survival. Remdesivir, an antiviral medication that was tested during the 2018 Ebola outbreak in the Congo, is being supplied by Gilead Sciences Inc. for emergency use under compassionate care conditions. A vaccine from the Sabin Vaccine Institute and an experimental therapy from privately held biotech Mapp Biopharmaceutical Inc. are also set to be tested in Rwanda, which has provided an emergency vaccine for frontline health workers. Sabin and Mapp have received more than $235 million and $129 million, respectively, in funding from the US Biomedical Advanced Research and Development Authority.
How is the current outbreak being managed?
There were 56 confirmed cases in Rwanda as of early October, making it one of the largest Marburg outbreaks. While the source of the infection is still under investigation, an outbreak in neighboring Tanzania last year was in a region that borders Rwanda. More than 300 contacts have been traced, with suspected cases being isolated and patients being cared for in hospitals. The Rwandan government is coordinating the response — with support from the Africa Centres for Disease Control and Prevention, WHO and other partners that are helping to ensure laboratory testing kits and PPE are being made available. Risk of international spread is heightened by confirmed cases being reported in Rwanda’s capital city, which has an international airport and road networks to several cities in the region. The United Nations health agency is working with nearby countries, including Democratic Republic of Congo, Burundi, Kenya, Tanzania and Uganda, to review their readiness to respond. An assessment of the risk for South Sudan, due to trade routes, is also being conducted.
Where else have cases occurred?
Since the initial cases among lab workers in Germany and former Yugoslavia in 1967, outbreaks have occurred in Ghana, Kenya, Congo, Angola, Uganda, South Africa and Guinea. A fatal case occurred in Russia in 1990 after a lab infection, and another in 2008 in a woman who had returned home to the Netherlands after visiting the Python Cave in Uganda’s Maramagambo Forest days earlier. Before the cases reported in Rwanda, the two most recent outbreaks were in Equatorial Guinea and Tanzania in the first half of last year.
--With assistance from Ashleigh Furlong and Antony Sguazzin.
©2024 Bloomberg L.P.