In February, a 23-year-old Tanzanian fisherman suddenly fell ill, having just returned from a busy trading outpost in the middle of Lake Victoria. Back at home in Bukoba, a district in northwestern Tanzania, he was hit by bouts of vomiting and diarrhea. He developed a fever and began bleeding from his body openings. On March 1, he died.

His family and community conducted a routine burial—not knowing this gathering would be the beginning of a deadly outbreak. Soon, some of those present began to fall ill. On March 16, Tanzania’s chief medical officer announced that an unknown, “possibly contagious” illness had been detected and deployed a rapid response team to Bukoba. Finally, five days later, PCR testing at Tanzania’s National Public Health Laboratory revealed the cause: Marburg virus.

This wasn’t the first appearance of Marburg this year. On February 13, Equatorial Guinea reported its first ever outbreak. A deadly virus, spreading in new places on opposite sides of the continent at the same time, is a big warning. It shows not just the ever-present threat of viruses spilling over from nature into humans, but that, yet again, the world isn’t prepared to deal with these dangers. 

Marburg shares plenty of characteristics with Ebola—the viruses are part of the same family. Like Ebola, it causes viral hemorrhagic fever, resulting in dangerous internal bleeding and organ damage. In some outbreaks, up to 90 percent of cases have been fatal; at the time of writing, five of the people in Tanzania’s eight confirmed cases have died. Symptoms take anywhere from a few days to three weeks to develop, and the virus can spread through human contact, particularly via body fluids of an infected person or corpse. Fruit-eating bats of the Rousettus family are the virus’s suspected host.

So similar are the symptoms that “in this village, most people believe it’s Ebola,” says Abela Kakuru, a resident of Ibaraizibu, which is a 10-minute drive from Bukoba’s affected villages. But there’s one big difference: Unlike with Ebola, no vaccines or antivirals have been approved for Marburg. Fluids, electrolytes, blood, and oxygen can be given to treat the symptoms, but there’s nothing yet to contain or fight the virus. “Supportive care to patients is the mainstay of treatment,” Tanzania’s minister of health, Ummy Mwalimu, said in a press briefing in late March.

Developing a vaccine thankfully doesn’t have to start from scratch. Several experimental vaccines have shown promise in nonhuman primates, and one from the Sabin Institute has also recently been tested in a small number of humans. It was found to be safe and to stimulate an immune response.

The World Health Organization is now planning to start trials of some of the experimental vaccines using what’s known as ring vaccination. “It means we will offer the vaccine to the close contacts of the cases,” says Ana-Maria Henao Restrepo, co-lead of the WHO’s R&D Blueprint for epidemics. “This is, in our experience, about 20 to 50 people, depending on the social network of each case.” Statistical analysis of how many contacts subsequently become infected should allow researchers to calculate how well the vaccines work. 

There aren’t large quantities of experimental vaccine doses readily available—just several thousand in total—but “we have sufficient doses to make rings around the contacts,” Henao Restrepo says. If some or all of the Marburg vaccines prove effective, the next step would be to create a stockpile for countries to use when they need them—as has been done for the most common form of Ebola.

This would patch up one hole in the Marburg response, but there are still others. In Tanzania, two weeks passed between the fisherman’s death and authorities announcing the spread of the then unknown illness. By that point, three of the fisherman’s family had also died from the virus. 

There needs to be better local testing: Without it, health workers and the public remain in the dark about what they are dealing with early on in an outbreak. Some protective measures were introduced in Bukoba—it was feared that the fisherman’s relatives might have Ebola, so they were buried under supervision by health workers in personal protective equipment, with no funeral gatherings. But had testing revealed the presence of a dangerous virus earlier, steps could have been taken to minimize the chances of the family members getting infected in the first place.

And if a virus like Marburg is spreading, being able to do genetic sequencing locally is particularly useful; it helps researchers keep track of any changes to the virus, and how these could affect patients. But in countries like Tanzania and Equatorial Guinea, sequencing capacity is limited. “Without knowing the variants, and subsequently how the virus is evolving, knowing the impact on health and severity will remain a challenge,” says Mohamed Zahir Alimohamed, a human genetics scientist at Tanzania’s Muhimbili University of Health and Allied Sciences.

When the fisherman’s relatives fell ill, they were admitted to the Maruku Health Centre in Bukoba. A lab technician who handled their samples caught the virus and died. And of the three surviving patients, one is a health worker. This suggests the local health services didn’t have sufficient protocols in place for dealing with potentially dangerous pathogens. “There is a need to be proactive, and to have [viral hemorrhagic fever] contingency plans,” says Loveness Isojick, an infection prevention and control nurse activity manager at Médecins Sans Frontières.

This, Isojick argues, needs to go beyond the basics of just infection control. “We need to look into ways of managing special cases, like pregnant women. What about the discharge package for the males who were positive, so that they do not infect their spouses after recovery?” she says. Marburg virus has been documented in the semen of male patients up to seven weeks after they have recovered. 

To date, no additional cases have been detected in Tanzania, and the outbreak hasn’t reached beyond Bukoba. One of the three patients receiving treatment has been discharged. The virus appears to be under control there. But in Equatorial Guinea, infections and deaths haven’t been contained. This can also be traced back to insufficient laboratory testing capabilities in the country. Early on in the outbreak, samples from suspected patients had to be taken to neighboring Gabon and Senegal for processing. Since then, reported confirmed cases have risen from one to 13, with nine patients dying. At least 20 probable cases—all resulting in death—have also been identified, and on top of this, the WHO has said that there are additional lab-confirmed cases in the country—but that these haven’t yet been officially reported. 

Worryingly, the confirmed cases are spread across three provinces, some 150 kilometers apart, suggesting viral transmission is happening undetected. The Ministry of Health has launched a public health emergency operation to contain the outbreak—but with better testing capacity early on, this might have happened much quicker.

It’s not just Marburg’s high fatality rate that makes it a grave concern, says Tanimola Akande, professor of public health at the University of Ilorin in Nigeria. “It has the potential to spread across borders.” Cases have been identified in Europe and the United States in the past, when tourists returned from holidays in East Africa. Indeed, the virus gets its name from the German city of Marburg, following an outbreak there in 1967 that contributed to its identification (though that outbreak originated from imported African green monkeys, not humans).

A big unanswered question is whether the current outbreaks in Tanzania and Equatorial Guinea are linked—the public health agency for the continent, the Africa Centers for Disease Control and Prevention, is running sequencing to find out. If the outbreaks are related, they illustrate how a future spillover event could easily cascade into a global outbreak if a pathogen isn’t contained and infected people travel overseas.

For now, in Tanzania, 205 people who may have had contact with the infected have been put under close monitoring. Meanwhile, health authorities are promoting measures in Bukoba to keep the virus from spreading (such as hand washing and social distancing), ensuring that any burials in the area are safe and highly supervised, and monitoring travelers leaving the wider region for symptoms. “We are scaling up awareness campaigns,” Mwalimu, the Tanzanian health minister, said during a press briefing.

In Equatorial Guinea, the full scale of the outbreak has yet to reveal itself—government reporting of cases has been slow, and the geographical spread of those logged so far suggests there’s been unreported transmission. To try to get on top of the virus, the government has the Emergency Response Plan for Marburg Virus Disease, developed with the WHO and Unicef. But this is a very limited set of actions—essentially the same as those being used in Tanzania: monitoring contacts of the infected and spreading the word about good hygiene practices. 

There are at least candidate vaccines for Marburg—and they are being tested during this outbreak. But if the current Marburg outbreaks had been bigger, the several thousand experimental doses ready to deploy wouldn’t have been enough to conduct ring vaccination. The virus is a known threat, but there aren’t abundant supplies of vaccines to test against it.

And what if the next pathogen to emerge is something that’s never been seen before, and there are no experimental vaccines available at all? If that happened, the world would be relying solely on quick testing and effective containment to stop the disease from spreading. As the Covid-19 pandemic showed—and Marburg is now underlining in Equatorial Guinea—this is something countries still need to get much, much better at. 

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