For decades, Dr. Daniel Bausch fought the world's most dangerous emerging tropical viruses directly from the trenches: He has trapped bats in Democratic Republic of Congo in search of the animal reservoir of Marburg virus. He has jumped into outbreaks of diseases such as dengue, yellow fever, Lassa fever and Ebola, spending months at a time treating patients in lower income countries ranging from El Salvador to Guinea. When NPR first spotlighted Bausch's efforts back in 2014, he had come off a stretch in Sierra Leone as one of only two doctors caring for 60 patients in an Ebola ward.

But now Bausch says of this work, "You realize that's all on the response side. And do we want to be responding forever? Putting on the band-aid each time something happens, and then the cycle of another outbreak begins?"

Increasingly, Bausch says, he's come to appreciate that, "the impact is with trying to change the system."

So, in 2021, Bausch switched tactics to focus on a long-neglected systemic challenge: Making sure that, at the first sign of an incipient outbreak, the world can come up with tests to diagnose people with the new disease – and make sure those tests are available not just in wealthy countries but in the lowest income ones.

In years past Bausch was employed in a series of frontline clinical and research posts with the United States Centers for Disease Control and Prevention and other key institutions. Today he is based in Geneva as senior adviser for Global Health Security at the non-profit FIND – one of the leading global organizations for developing diagnostic tests. This week he traveled for meetings in Washington, D.C., where NPR caught up with him. This conversation has been lightly edited for length and clarity.

Here are eight takeaways.

We can't prevent the next pandemic unless we're ready with diagnostics.

It's "one of the key aspects of preparedness," says Bausch. "We can say we need to have great surveillance systems. But if someone comes and says, 'A bunch of people have a fever and a headache, but I don't have a diagnostic test to know what's causing it,' that won't really get us far."

"Diagnostics are at the foundation. We won't know what vaccines to develop or what therapeutics to develop if we don't know what people have in the first place."

Yet developing diagnostics has not been a global priority.

"It's been very vaccine-oriented – there's a lot of focus on vaccines and some focus on therapeutics," says Bausch. "And of course I don't disagree with that," he adds. "We need vaccines and therapeutics." But, he says, "Diagnostics are often the ignored component of this. It's an area that people just haven't been focused on too much."

There's already a shocking lack of access to existing tests.

Among the consequences of this neglect, says Bausch, is that many people in low-income countries can't even get hold of existing diagnostic tests.

"Most of the people in the world who are sick or dying of something don't actually know what they have," says Bausch. "And it's not only these – if you will – 'exotic' viruses like Ebola and Marburg and Lassa," for which the diagnostic options are not particularly good. "Most people don't know if they have tuberculosis or diabetes or hypertension," he says. "The diagnostic gap, especially at the primary health-care level in low income countries, is huge."

"And I mean we know how to test someone for diabetes," adds Bausch. Yet "if you look at how many people who have diabetes, know that they have diabetes – it's less than 50% in many low- and middle-income countries."

This equity gap on testing mainly comes down to economics ...

"Cost certainly is one of the impediments here," says Bausch. A company, "can have a great diagnostic test. But if it costs $100 per test – well, it's not going to be put in place in Democratic Republic of Congo."

This dynamic also discourages pharmaceutical companies from trying to develop new tests for diseases that are only prevalent in low-income countries. Diagnostic makers "ultimately do have a bottom line, right?" says Bausch. "They can't just give it away."

So while he's been finding it relatively easy to convince them to focus on "truly pandemic-prone diseases where the potential market is huge," he says he's faced an uphill battle on diseases limited to "a very poor population, in a relatively poor country, who may have a very big need for a product but don't have a lot of money to spend on it."

The recent outbreak of mpox is a classic example, he adds. "Once it hit richer countries outside of Africa there was lots of interest," he says. "Now the cases are going down in those [wealthier] places. But the virus is still in Central and West Africa, causing significant disease." The challenge, however, is that the number of people affected is "not in the hundreds of thousands. So if you're purely basing it on economics you say, 'Okay, Well why would I develop a test for that? How much would it be used?' We're in this sort of no man's land where it's been hard to get test makers engaged."

... and logistical hurdles

Another difficulty is that, because low- and middle-income countries are "not where pharmaceutical companies traditionally have been able to make money," the test makers are often not set up to export to those markets even when it does make financial sense.

"If you want to have your product sold in Nairobi, Kenya, or Dakar, Senegal, it doesn't just appear," notes Bausch. You have to set up a pipeline – including getting the test approved by regulatory agencies. "In many low- and middle-income countries, those agencies are relatively new." says Bausch. "They're not used to this and there can be long delays."

So the solution lies with economics and logistics too.

Bausch says the upshot of all this is that while some of FIND's work is technical and research-oriented, a major focus is tackling the economic and logistical hurdles to diagnostic development. Working with partners such as the World Bank, Africa's Center for Disease Control and Prevention, and ministries of health "to think of more creative financing strategies like advance purchasing agreements that encourage pharmaceutical companies to get into the game because you say to them, 'If you create this test, we will buy this much. So there will be less risk to you.'"

Bausch says FIND is also working to support test makers based directly in low- and middle-income regions. "There's one in Dakar called DIATROPIX "that's trying to figure out what its sweet spot can be. It has no interest, of course, in getting into competition with huge diagnostic makers [in wealthy countries] that can sell tests for pennies. But there may be a niche for it in making products that a huge diagnostic maker [might] not consider has a large enough market."

There's been some "exciting" scientific progress.

Despite all the obstacles, Bausch says he's "excited" by several recent scientific developments in the field of diagnostics.

Across the globe, the pandemic has dramatically increased people's familiarity – and comfort – with at-home tests. Bausch says if this model can be widely adopted for diseases beyond COVID, it could vastly speed up diagnoses.

Test makers have also been developing ever more sophisticated "molecular multiplex assays" – essentially tests for multiple viruses bundled into a single diagnostic.

That would be hugely helpful in low income countries, says Bausch. "I can tell you from years in Ebola outbreaks, being the clinician taking care of the patient, if you go in and say, 'Good news, your Ebola test is negative,' the patient smiles for a minute. but of course then they want to know what they do have. To say, 'You're still dying of something. But we don't know what it is,' is not very comforting."

Fortunately these multiplex tests are "getting down to a price point of a few dollars a test," says Bausch.

"It exists, and now getting into greater use in low and middle income countries is the next step."

Look to low income countries to lead.

NPR concluded this interview by noting that – when we spoke with Bausch back in 2014, shortly after he had returned from his time responding to the Ebola crisis in Sierra Leone, he had offered an interesting analogy for the experience: "It's like saying, 'Well, you've trained somebody to be a pilot,' " he had said then. "So, 'There's the plane. Go fly the plane.' Without thinking: What about mechanics? What about the other people who have to guide the plane down the runway? You don't have all the very important supporting personnel that you need for [Ebola], and so it's been a tragic situation."

So we asked Bausch: Nine years later, does this still hold true in Africa?

His answer is encouraging:

"The architecture for outbreak response has changed drastically," he says. "When we have outbreaks of Ebola in places like the Democratic Republic of the Congo, colleagues at the main research institute there, they're very experienced now with this."

"It doesn't mean that they don't need – nor receive – any support," Bausch adds. "But they have gotten this down and figured it out. So things happen much more independently than they did [before]."

"No longer – and this is a good thing — no longer should anybody from the U.S. CDC or the World Health Organization or London or Geneva or anywhere else think, 'Okay, We're going to come in and tell people what to do.' Those of us who are not from that area of the world really need to recognize that we're there to play an important but a supporting role in the leadership that's going to come from the African continent."