The year was 2017. Polio — officially certified as eliminated from Europe in 2002 — was not supposed to be an airport security concern. And yet, at Warsaw Chopin International Airport, a team of Polish public health researchers began methodically collecting wastewater from flights arriving from countries with known or suspected poliovirus circulation.

What they found changed how Europe thinks about airport surveillance.

The study

Between 2017 and 2020, researchers from the National Institute of Public Health in Poland systematically sampled airport wastewater at Warsaw Chopin Airport [1]. The study — published in Eurosurveillance, the European Centre for Disease Prevention and Control's peer-reviewed journal — targeted flights arriving from regions where Wild Poliovirus Type 1 (WPV1) or circulating Vaccine-Derived Poliovirus (cVDPV) was known to be endemic or actively circulating: primarily parts of South Asia and Africa.

The sampling protocol was straightforward: wastewater was collected from lavatory service vehicles after emptying the holding tanks of inbound international aircraft. Samples were concentrated and tested for poliovirus RNA using RT-PCR, with positive samples sequenced for lineage identification.

On multiple occasions across the study period, poliovirus RNA was detected. The airport wastewater surveillance system was functioning as a sentinel — catching imported poliovirus in inbound flight waste before it could manifest clinically in the Polish population.

Why polio in aircraft wastewater matters

Polio is primarily a disease of the gastrointestinal tract. The poliovirus replicates in the gut and is shed in faeces at very high concentrations — for weeks, in some cases — including by individuals who develop no paralytic symptoms. Infected individuals are most contagious precisely when they are asymptomatic and have no reason to avoid travel.

This biology makes poliovirus an ideal target for wastewater surveillance: the primary excretion route is faecal, the concentrations are high, and the infected individual shows no outward sign that clinical screening would detect.

Polio was supposed to be a solved problem. It was certified eliminated from Europe. And then it came back — through airports, through travellers, through the same routes that every pathogen uses. The Poland study did not discover something new about polio. It discovered something new about airports: they are where re-emerging diseases first declare themselves.

Polio's return — and the airport connection

The Poland study was prescient. In 2022 and 2023, poliovirus re-emerged in exactly the pattern their surveillance was designed to catch:

United Kingdom, 2022. The UK Health Security Agency detected poliovirus in London's sewage network — the first evidence of domestic transmission since 1984. The strain was a circulating vaccine-derived poliovirus (cVDPV2), linked to international travellers. The UK subsequently launched an emergency vaccination programme for children in affected London boroughs.

United States, 2022. An unvaccinated adult in Rockland County, New York, was diagnosed with paralytic polio — the first US case since 2013. Subsequent wastewater sampling in New York found poliovirus in sewage, indicating broader silent circulation in the community before the clinical case was identified. The patient's strain was linked to travellers who had passed through the area.

In both cases, the virus had been silently imported — carried by travellers who showed no symptoms — before appearing in community wastewater and eventually clinical cases. In both cases, airport-level surveillance would have been the earliest possible detection point.

What this means beyond COVID-19

The dominant framing of aircraft wastewater surveillance has been COVID-19. This is understandable — the pandemic created the political will and funding to build these systems — but it is a limiting frame.

Poliovirus, measles, Mpox, cholera, and antimicrobial-resistant bacteria all share the same basic property as SARS-CoV-2 with respect to wastewater surveillance: they are shed in human waste and detectable by molecular methods. An aircraft wastewater surveillance system built for one pathogen is, with appropriate panel design, a system for all of them.

The Poland study is the clearest demonstration that this is not a COVID-era innovation. It is a permanent, multi-pathogen border health infrastructure that was technically feasible before COVID-19 existed, and that remains necessary long after COVID-19 has receded in public attention.

The Thailand context

Southeast Asia remains among the highest-risk regions globally for poliovirus importation from endemic areas. The region connects through aviation to Pakistan, Afghanistan, and parts of Africa where WPV1 continues to circulate. Suvarnabhumi handles direct and connecting flights from all of these regions.

Thailand's domestic polio vaccination coverage is high, which reduces the risk of paralytic disease. But vaccination does not prevent the virus from circulating silently in partially-immune populations — as London's 2022 experience demonstrated. And surveillance for poliovirus importation via aviation currently does not exist in Thailand.

An AWSS panel that includes poliovirus alongside SARS-CoV-2, influenza, and the other 30+ detectable targets would provide exactly the kind of integrated early warning that the Poland study was designed to demonstrate is possible. The science is settled. The methodology is published. The question is whether Thailand's aviation health infrastructure will build it before the next imported poliovirus case appears — or after.