1112: Inside Traveler-Based Genomic Surveillance

JOHN SHEEHAN:
This is Public Health Review Morning Edition for Thursday, April 23, 2026. I'm John Sheehan with news from the Association of State and Territorial Health Officials.

Today: how public health officials are detecting emerging viruses before they spread widely across the U.S. Heather Reese, genomic epidemiology and preparedness team lead at CDC, tells us about the Traveler-Based Genomic Surveillance program, a cutting-edge effort that turns international travel into an early warning system for public health threats.

Heather Reese, welcome to the show.

HEATHER REESE:
Thanks for having me on.

SHEEHAN:

So, Heather, set this up for us. What is the Traveler-Based Genomic Surveillance program?

REESE:

The Traveler-Based Genomic Surveillance program, or TGS, is a public health program that monitors for pathogens of public health concern and emerging strains or variants in inbound international travelers arriving at select U.S. airports. So, the program actually consists of three complementary approaches. The first is volunteering anonymous nasal sampling of those inbound international air travelers arriving at select U.S. airports where TGS operates. The program also includes aircraft wastewater sampling. So, we collect wastewater directly from individual airplanes arriving from international locations, and also from the airport triturator, which gives us a pooled aircraft wastewater sample. So, together, these samples, the nasal swabs and the wastewater samples, are tested for several different pathogens of public health concern, which include SARS-CoV-2, flu, RSV. Those that test positive for COVID and flu are sequenced, and together, all of those data allow for timely detection of those pathogens of public health concern, and allow us to track emerging strains and variants, and fill gaps in global biosurveillance.

SHEEHAN:

That's really interesting. So, you're using nasal swabs and wastewater testing?

REESE:

Yes, absolutely. We get some passenger travel information, so where they've traveled through recently, and that's paired with the test results on what they test positive for. And that gives us that specific geography of what might be circulating globally in that area. And then the wastewater data gives us more of a landscape view. So, it's all the travelers who used the toilet while they were on board the aircraft for our individual wastewater samples. And then for our combined aircraft wastewater samples, that gives us a nice, efficient sample for all the aircraft wastewater that was deposited into a triturator within a 24-hour period. So, it really gives us kind of a nice landscape view of everything that might be circulating and coming in through that airport.

SHEEHAN:

And the program just surpassed a million voluntary participants. What does it mean to have that kind of scale of people who are contributing to that surveillance?

REESE:

Reaching one million international traveler participants since the program started in 2021 is a significant milestone. This really means the public is interested in supporting public health and disease detection, which allows us to react faster to incoming disease threats. So, the program really wouldn't be possible without the contributions of those travelers.

SHEEHAN:

And can you connect the dots for us for how when you're sampling these international travelers and how that filters down to what you can expect or at least be prepared for on the state and local level?

REESE:

So, to start with, U.S. airports are visited by more than 100 million international travelers each year. Previous global outbreaks have shown that diseases move easily across borders. So, an emerging disease threat anywhere is the potential for a disease threat everywhere. The TGS program really allows us to use that air travel network for timely detection of pathogens and public health concerns, and allows us to track for emerging strains or variants as international travelers land at the airport. And that's often before these specific pathogens or these specific new lineages are circulating broadly within U.S. communities. Since the program collects data from travelers arriving from over 130 countries each week, this can help fill gaps in global biosurveillance and can give both CDC, and us at a national level, as well as at a state level, a glimpse of what might be coming soon to the U.S.

SHEEHAN:

Yeah. And speaking of timely detection, what kind of heads up does it give you? Are you turning the wastewater around in a matter of days? Is it hours? And can you talk about the importance of having that preparation?

REESE:

So, we test for a variety of pathogens using PCR on both our nasal and our wastewater data. Those results are within a matter of days. I mentioned previously, we also sequence for SARS-CoV-2 and flu, which allows us to really get a better sense, as those pathogens evolve, what might be a concerning variant or lineage. That sequence data is a little around, you know, a week and a half. It's usually under two-week turnaround time there. We recently had a detection that really showed the value of TGS and the timeliness. So, this past summer, TGS, together with CDC's influenza scientists, identified and reported the first two sequences of flu H3N2 Subclade K globally. So, at that time, there was increased flu activity globally, but this was before the flu season had really started in the U.S. And because of those early subclade K detections, and arriving international travelers, the CDC was on alert for domestic cases. We were able to prepare public health and health care providers to expect to see eventual cases. And it also accelerated CDC and public health laboratory access to samples of that subclade K virus. That allows us for additional genomic characterization to assess potential impacts on diagnostics, therapeutics, and even vaccine. And so, access to those data has also supported research efforts for influenza antibody response. So, not only do our data, PCR and sequencing data, have a pretty timely turnaround, we also make our sequence data available publicly in public sequence repositories. That means that the broader scientific and research community also has the ability to get access to those data early and contribute to broader scientific knowledge.

SHEEHAN:

That's amazing. That really describes how it's an important surveillance method not just for a possible next pandemic, but this is really just the broader state of what's coming into the population. I mean, it impacts people on a day-to-day basis.

REESE:

It's a very nimble and flexible program. We have a panel of pathogens of public health concern that we're monitoring for on a daily basis, as inbound international travelers volunteer to participate, and as we collect samples from aircraft. And it allows us to be constantly scanning for, you know, what, if there's going to be a significant evolutionary shift in, as I mentioned, you know, the flu A subclade K was a really significant evolutionary shift. And it allows us to start monitoring to see if there are true public health impacts to that shift, but it also allows us to fill gaps in global biosurveillance. So, an idea of what might be circulating in another part of the world, and has the potential to impact U.S. communities.

SHEEHAN:

What would you say are the big takeaways of the program? It sounds like it's really helping just give a better picture of surveillance overall, especially with, you know, not just in a single population, but how viruses move between populations.

REESE:

Yes. So, I think that what we've found that's really important about TGS is it takes advantage of the global air travel network. And with the contribution of, you know, the international travelers who volunteer to participate, it really allows us to detect new public health threats early, respond faster, and protect our communities. And I'd say just one other piece is if you are traveling, you're returning from an international trip, and you're coming through one of the airports where TGS operates, we would love if you would volunteer to participate. This program really wouldn't be possible without that.

SHEEHAN:

Heather Reese, thanks so much.

REESE:

Thank you so much for having me on.

SHEEHAN:

Heather Reese is genomic epidemiology and preparedness team lead at CDC.

An upcoming webinar provides an in-depth walk-through of the ASTHO report, "Driving Impact with Flexible Funding." Participants will explore how state health agencies can move beyond traditional funding silos to create more agile, high-impact public health initiatives. Through real-world examples and strategic analysis, we will examine the pathways to successfully adopting and expanding flexible funding models in a governmental setting. Find the link in the show notes.

Public health agencies must be administratively ready to fulfill core functions, respond capably to public health emergencies, and utilize funds efficiently and effectively to improve health outcomes. Administrative readiness also depends on an organization's ability to navigate challenges and ensure operational continuity in a complex and uncertain environment. Find the link to the new blog post, "How Public Health Can Support Modern Administrative Readiness in a Dynamic World," in the show notes.

This has been Public Health Review Morning Edition. I'm John Sheehan for the Association of State and Territorial Health Officials.