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On September 27, 2024, the world learned that Marburg virus -- a close cousin of Ebola -- had in Kigali, Rwanda, where it was largely sickening healthcare workers in two hospitals. By September 30, Marburg had already . As of October 7, Rwanda's government stated that had reached at least 56 confirmed infections and 12 deaths.

"Out of an abundance of caution," the CDC announced a plan to arriving from Rwanda starting the week of October 14. Meanwhile, the Sabin Institute of an experimental Marburg vaccine for use in high-risk medical workers and others in six sites in the country.

Marburg's pleomorphic virions -- often resembling rods, rings, or the number 6 -- were first identified in 1967 when the agent killed German and Serbian researchers exposed to infected monkeys imported from Africa. Today, lists only one subsequent Marburg illness in a lab worker in Russia, and fewer than 10 cases in non-African travelers to the continent or their close contacts. The story in Africa looks quite different: between 1975 and the present, small and large outbreaks of Marburg with case-fatality rates of 24%-to-88% occurring in Angola, Democratic Republic of the Congo (DRC), Equatorial Guinea, Ghana, Kenya, South Africa, Tanzania, and Uganda have officially and possibly many more.

For further reflections on Marburg's latest assault and the world's continuing need for tests and vaccines to contain it, I recently spoke with Daniel Bausch, MD, MPH&TM, a past-president of the American Society of Tropical Medicine and Hygiene, whose experience with hemorrhagic fevers spans three decades. Bausch previously led CDC's and the World Health Organization's (WHO) Lassa Fever program in Africa, ran Ebola treatment centers in Uganda and Sierra Leone, investigated hantavirus infections in Bolivia, and trapped fruit bats (the presumed reservoir host of Marburg) in DRC. From 2019 to 2022, Bausch served as a co-principal investigator for an Ebola vaccine trial in Northern Kivu Province, Eastern DRC.

A Surprising Place to Surface?

"We've never seen Marburg before in Rwanda," was one of the first things Bausch told me in late September, "but [since] we have seen cases in surrounding countries, that's only sort of surprising."

Bausch was more concerned about piecing together the details of the Rwanda outbreak's index case. "The usual thing," he said, "is for someone to explore a cave or work in a mine where they are exposed to the virus through contact with bat excreta, then get sick and infect a few other people. That's usually where it ends."

But, to Bausch, the most remarkable feature of Rwanda's outbreak is its high rate of , since healthcare workers initially comprised . "I haven't worked in hospitals in Rwanda," Bausch said, "...nevertheless, [the country] is a kind of miracle. Things are really rough in DRC: you go to hospitals there, and there's no soap or running water...the IPC [infection prevention and control] is pretty poor." In comparison, Bausch described Rwanda as a place with air-conditioned airports, high-rise buildings, and cappuccino bars -- reflections of technology and development that made him surprised that the country did not fare better during the early stages of the current outbreak.

Nonetheless, Ebola's largest-ever rampage (centered in West Africa between late 2013 and 2016, with and more than 11,000 deaths), taught Bausch that, paradoxically, healthcare workers treating their own sometimes take surprising and unacceptable risks.

Insights from Sierra Leone

Now let's flash back to Kenema, Sierra Leone circa 2014 when Bausch had many people on his team who had previously worked in the country's Lassa Fever Unit. "It was almost like some surrealistic nightmare in which I dreamed that all these people I knew would come to me and say, 'I have a headache and fever,' then test positive for Ebola and become patients and die," Bausch said.

"One day, a nurse was sick with a suspected infection, and I entered the ward and one of the laboratory workers who I'd known for a long time was trying to start her IV," he continued. "I think he was only wearing gloves while I was in full PPE. And I said, 'What the hell are you doing?' to which he replied, 'That's my colleague.' And I said, 'Of course she is, but get out of here.' And he actually did contract Ebola and died, although I can't say if it was through that exposure."

"So, it does make me wonder what healthcare workers in Rwanda [who are currently infected] may have done because they wanted so much to treat a person they were close to," said Bausch. "Or sometimes it's just a particular event where something bad happens -- an IV comes out, or somebody has extensive hemorrhage, or there's an urgent need to intubate with no time to be as careful as one should. Or perhaps resources are lacking, although once again, one would expect that to be less of a problem in Rwanda."

"But I just don't know. 70% of 26 cases? That's a lot of people to be attending an urgent event," Bausch grimly concluded.

Of Vaccine Trials and Moral Imperatives

My conversation with Bausch also touched on reasons, both strategic and moral, for richer countries to support vaccine trials for far-flung, emerging killers like Marburg. But first to the trials themselves.

"Will a vaccine trial actually happen in Rwanda?" I asked him.

"Most of the time, when these events occur and we rush in and say we have to do a clinical trial, we're always too slow," Bausch replied. "But [the work] still has utility because of all the processes you go through dealing with cold chain and regulatory approvals and which products would be used and the [available] supply from whomever makes that particular product."

"We really have to think of these as longitudinal trials that happen across outbreaks," he continued. "Ironically, you always hope that the outbreak will be controlled before you can accrue enough cases to figure out if a drug or vaccine works, but even if so, the effort alone still has value, making you better prepared for the next time."

What about the cost? I pushed, recalling the millions of dollars spent on a trial of a new Ebola vaccine in DRC that Bausch helped to spearhead.

"I worked through this years ago because of my work in the U.S. and the U.K and people saying, 'Why should my hard-earned U.S. tax dollars or British pounds go to someone else's problem? I'm not African, I'm not Congolese, I'm not Rwandan. Why do I have to care?'" Bausch said. "And I always have two answers...both true. The first one is ethical. When something really bad is happening to someone else and we can help them, we should do our best to do it. At the same time, I realize that's not going to win the day for everyone ...especially the politicians and others who have to keep their eye on the bottom line."

"So my next argument is that you may not care about what's happening in Rwanda, but you do care about what's happening in London or New York or wherever," he said. "And the way to protect yourself is to go to the source."

"Here's the best example I've come up with," he added. "If you leave your house and see that a house down the block is burning, your best way to protect your own house -- even if you don't care about those other people -- is not to wait by your door with a bucket of water. The best thing to do is to go down the block and put that fire out."

Right now, of course, it's still too soon to know if Rwanda's viral blaze will breach national or international borders. But thousands of miles away, do we still need to prepare to safely care for infected people and invest in an effective Marburg vaccine? You'd better believe it.

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