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 triterator, 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, a
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 concern 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 from 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. Yeah.

SHEEHAN:

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 the 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 healthcare 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 in to 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 us 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, 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 walkthrough 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.