Airplane Wastewater Surveillance Detects SARS-CoV-2 Variants Weeks Before Clinical Systems
核心洞察
A bilateral US-UK pilot demonstrated that airplane wastewater can be collected and analyzed to track respiratory and enteric pathogens across international borders.
Norovirus GII (搜索) showed the highest detection proportion (approximately 80%) on UK-origin flights, followed by SARS-CoV-2 (搜索) and norovirus GI (搜索).
The SARS-CoV-2 (搜索) XEC variant was detected four weeks earlier on UK-origin flights than on US-origin flights, underscoring wastewater sampling's early-warning value.
A bilateral US-UK pilot study has demonstrated that wastewater collected from airplanes can serve as a feasible tool for tracking pathogen movement through international travel, offering an early-warning mechanism that may detect emerging variants before they surface in routine clinical surveillance.
The study, published online as an "Article in Press" in the journal Scientific Reports, evaluated the feasibility of monitoring wastewater from airplanes at two connected international airports in the United Kingdom and the United States. Wastewater samples were collected from flights operated by two airlines along a common transatlantic route, with one sample collected per flight from lavatory waste tanks during post-arrival servicing.
Study Design and Methodology
UK-origin flights were sampled at the US airport between March 27, 2024, and January 16, 2025, while US-origin flights were sampled at the UK airport between July 22, 2024, and January 15, 2025. Pathogen testing was performed using digital polymerase chain reaction (dPCR) in the US and quantitative polymerase chain reaction (qPCR) in the UK. For qPCR, samples with any amplification were considered positive, while for dPCR, samples with at least one positive partition were considered positive. All SARS-CoV-2 (搜索)-positive samples were further submitted for whole-genome sequencing, with genome recovery depending on viral concentration and sequencing coverage.
The study collected 308 wastewater samples from UK flights and 116 from US flights. Overall, 317 samples were positive for at least one targeted respiratory pathogen—SARS-CoV-2 (搜索), influenza A virus (搜索), respiratory syncytial virus (搜索), or influenza B virus (搜索)—while 303 were positive for at least one targeted enteric pathogen: adenovirus (搜索), norovirus GI (搜索), or norovirus GII (搜索).
Key Findings
Norovirus GII (搜索) had the highest detection proportion on UK-origin flights, at approximately 80%, followed by SARS-CoV-2 (搜索) and norovirus GI (搜索). US-origin flights showed lower detection rates, although the researchers noted that direct comparisons were limited by differences in laboratory methods, assay sensitivity, and positivity thresholds. Influenza A virus (搜索) detection was more frequent on flights originating in both countries at the end of 2024, consistent with seasonal patterns.
For SARS-CoV-2 (搜索), dPCR results were evaluated under a standard threshold (at least one positive partition) and a more stringent threshold (at least three positive partitions). Among samples positive under the standard threshold but negative under the stringent threshold, most (81%) produced sequencing data covering at least 25% of the SARS-CoV-2 genome at a minimum 10-fold depth. No SARS-CoV-2 sequences were recovered from the 64 sequenced samples that were negative under both thresholds.
The researchers observed similar patterns in SARS-CoV-2 (搜索) lineage frequencies in both directions, with KP.3.1.1 being the most common. However, UK-origin flights showed greater diversity of SARS-CoV-2 lineages, including LB.1 and JN.1.18, which were not detected on US-origin flights—though unequal sequencing coverage and sampling periods may have contributed to this difference.
Notably, the SARS-CoV-2 (搜索) XEC variant, designated as a variant under monitoring on September 24, 2024, was detected four weeks earlier on UK-origin flights (from September 17, 2024) than on US-origin flights (from October 14, 2024).
Early-Warning Potential in South Africa
The value of aircraft wastewater surveillance as an early-warning system is further underscored by work at South Africa's National Institute for Communicable Diseases (NICD). At Johannesburg's OR Tambo International Airport, which handles about 21 million passengers every year, researchers collect wastewater directly from aircraft lavatory tanks, airport terminal buildings, and a nearby manhole capturing wastewater from the airport community.
The NICD currently tests samples for SARS-CoV-2 (搜索), influenza A and B, measles (搜索), and mpox (搜索), carrying out genomic sequencing where appropriate. Their findings show that most aircraft wastewater samples contain SARS-CoV-2, confirming the virus is still circulating globally. Around 22% of aircraft samples test positive for SARS-CoV-2, while about 7% are positive for influenza A, with a similar proportion containing measles virus.
One finding stands out: the NICD detected the XFG SARS-CoV-2 (搜索) variant in aircraft wastewater 12 weeks before it was identified through South Africa's clinical surveillance system, before a case had been detected in a hospital or clinic, and around 24 weeks before it appeared in community wastewater surveillance.
"The earlier we detect a new pathogen or variant, the more time public health authorities have to understand the risk, strengthen surveillance where needed, and prepare an appropriate response," the NICD researchers noted.
Limitations and Future Directions
The authors of the US-UK pilot acknowledged several limitations. The study involved only two connected airports and two airlines, used different laboratory methods, lacked field blanks, and could not estimate infection prevalence among all passengers because airplane wastewater reflects only lavatory users who shed detectable genetic material. Assay inhibition and residual tank waste were also not fully assessed.
Despite these constraints, the recovery of SARS-CoV-2 (搜索) Omicron lineages LB.1 and JN.1.18, and the earlier detection of the XEC variant, underscore that aviation wastewater sampling may help capture timely lineage movement. The researchers concluded that broader airport coverage and standardized testing remain key to realizing the full potential of an international wastewater surveillance network.