For decades, Stephen Morse, PhD, has been asking a deceptively simple question: How do we prepare for an infectious disease threat we don’t yet know exists?
Long before COVID-19, Morse helped shape the modern understanding of emerging infectious diseases. An epidemiologist, researcher, and longtime leader in the field, he coined the term “emerging viruses” and edited the landmark 1993 book Emerging Viruses. His career has spanned laboratory virology, epidemiology, biodefense, surveillance, and public health—giving him a unique perspective on how our understanding of emerging pathogens has changed and where preparedness still falls short.
In a recent episode of Transmission Interrupted, host Jill Morgan, RN, talks with Morse about the origins of the emerging infections field, what decades of outbreaks have taught us, and why preparing for the next threat requires something more difficult than predicting which pathogen will cause it.
In the mid-20th century, optimism about antibiotics, vaccines, sanitation, and other public health advances led some to believe that infectious diseases might eventually become a problem of the past.
Then came HIV.
HIV demonstrated not only the devastating potential of a previously unrecognized human pathogen but also how much remained unknown about the diversity of infectious diseases. For Morse, it helped raise a larger question: Where do new infectious diseases come from?
In the late 1980s, Morse and colleagues began bringing together scientists with different perspectives to explore that question. Some focused on viral evolution. Others studied pathogens in animals and the environment.
Over time, a clearer picture emerged. Many emerging infections are zoonotic, originating in animals before crossing into humans. Changes in land use, agriculture, human behavior, travel, and other forms of environmental and societal change can create new opportunities for those pathogens to reach people and spread.
Globalization can then turn what was once a geographically limited event into a much broader threat.
“We’re always moving and always changing the environment,” Morse explains. Those changes can have unintended consequences, creating new opportunities for pathogens and people to meet.
Preparedness efforts often begin with lists: Which pathogens pose the greatest threat? Which diseases are most likely to cause the next outbreak or pandemic?
Morse cautions against allowing those lists to define preparedness.
Influenza has long been an obvious pandemic concern. Smallpox and anthrax have played important roles in biodefense planning. Yet SARS-CoV-2 demonstrated how a threat outside the expected scenarios could transform the world.
The goal, Morse says, should be to create a framework that allows us to recognize and respond to something we have not anticipated.
“The whole idea was to think about how do you become prepared for surprise,” he says.
That means maintaining pathogen-specific expertise while also building flexible capabilities—surveillance, diagnostics, infection prevention, trained healthcare teams, communication systems, and public health infrastructure—that can be adapted when the threat does not look exactly like the one in the exercise plan.
That philosophy also shaped Morse’s work at the Defense Advanced Research Projects Agency (DARPA), where he was among the early scientists helping expand the agency’s work into biology.
Rather than developing defenses against only individual pathogens, researchers explored approaches that could potentially work across multiple threats. That included studying common mechanisms pathogens use to cause disease, strengthening immune responses, improving diagnostics, and identifying infection earlier.
The goal was ambitious: develop capabilities that might still be useful even when the specific pathogen was not known in advance.
Some of the technologies explored through this work helped contribute to diagnostic approaches that are now familiar, including nanopore sequencing and rapid molecular diagnostic platforms.
The underlying idea remains highly relevant to special pathogen preparedness today: build capabilities that are useful across threats rather than waiting until a crisis to develop a solution for a single disease.
After nearly every major outbreak or pandemic, healthcare and public health leaders identify lessons learned. The harder part, Morse argues, is sustaining the urgency needed to put those lessons into practice.
“One thing that does worry me is … a lack of imagination, a lack of urgency, and a lack of ability to sustain momentum,” he says.
Morse points to Ebola, COVID-19, and mpox as examples of events that exposed persistent gaps despite years of preparedness planning.
That is also why sustained healthcare preparedness infrastructure matters. During the conversation, Morse highlights the importance of NETEC and the network of healthcare facilities prepared to identify, isolate, and care for patients with high-consequence infectious diseases.
Training is particularly important when teams are preparing for events they may rarely encounter. PPE is one example: having the equipment is only part of preparedness. Healthcare workers must also be trained and practiced in using it safely.
The shortages experienced during COVID-19 offered another lesson. Morse recalls healthcare workers struggling to obtain basic respiratory protection and discussions about how to reuse N95 respirators.
“We should never have had that discussion,” he says. “They should have been as plentiful as in fact they are today.”
One of the themes that has followed Morse throughout his career is the importance of disease surveillance.
Following the 1989 conference that helped establish the emerging infections field, Morse and colleagues helped launch the Program for Monitoring Emerging Diseases, or ProMED. What began as an email-based network became an early example of using emerging communications technology to share information about infectious disease events around the world.
Today, the technological capabilities available for surveillance are dramatically more sophisticated. Scientists can rapidly sequence pathogens, identify previously unknown organisms, and communicate findings around the world almost instantaneously.
But technology alone does not equal preparedness.
“Surveillance is information for action,” Morse says.
Knowing that an outbreak is occurring—and even knowing where it is spreading—matters only if systems are prepared to respond to that information.
For Morse, that means pairing surveillance with plans, tools, communication, education, and public health measures that can slow transmission before an outbreak becomes a much larger crisis.
More than three decades after Morse helped introduce the concept of emerging viruses, the fundamental challenge remains remarkably similar.
Pathogens continue to cross species. Human activity continues to change the environments in which those pathogens circulate. International travel can move an infection across the world quickly. And evolution ensures that pathogens themselves will continue to change.
We may have better diagnostics, faster sequencing, more sophisticated surveillance systems, and decades of experience responding to HIV, Ebola, COVID-19, mpox, and other infectious disease threats.
But the next major threat may still surprise us.
For Morse, that uncertainty is precisely why preparedness matters.
Rather than trying to perfectly predict what comes next, healthcare and public health systems can invest in the capabilities that allow them to recognize unusual events early, communicate quickly, protect healthcare workers, care safely for patients, and act on the information they receive.
As Morse puts it, the greatest concern may not be any one pathogen, but losing the imagination and urgency needed to prepare for something we have never seen before.
Listen to the full episode of Transmission Interrupted to hear Jill Morgan’s conversation with Stephen Morse, PhD, about emerging infections, surveillance, pandemic preparedness, and what decades of outbreaks can teach us about preparing for whatever comes next.
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Preparing for the Pathogen We Can’t Predict: Lessons from Dr. Stephen Morse – National Emerging Special Pathogens Training & Education Center
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