This study evaluated a locally implemented wastewater surveillance (WS) system for respiratory viruses in Bethel, Alaska, from October 19, 2022, through May 31, 2024. The WS program integrated routine sewage sampling, on-site molecular testing for multiple respiratory viruses, and comparison with clinical testing data from the regional hospital laboratory. Data reported include results from 318 wastewater samples and 7,392 clinical respiratory virus tests.
Bethel is a regional hub in southwestern Alaska with approximately 6,300 residents in 2,450 households; 74% of residents identify as Alaska Native. The town serves the surrounding region’s ~22,000 residents because it houses the region’s only hospital and transportation hub. Wastewater infrastructure in Bethel includes a central piped sewer system serving 479 customers and a broader truck-hauled system serving 1,373 customers. The piped system accounts for roughly 25% of connections but produces about 65% of wastewater volume, whereas hauled customers account for 75% of connections but produce about 35% of volume.
Sampling targeted Bethel’s last lift station, which pumps raw sewage onward to the sewage lagoon. Approximately 90% of piped wastewater passes that lift station, including wastewater from the YK Delta Regional Hospital and long-term care facilities; about 50% of hauled sewage also passes through that pumping point. Prior local evidence indicated stronger viral signals from lift station samples compared with lagoon samples, motivating the chosen sampling site.
Investigators used passive Moore swab sampling during October 2022–May 2024. Sampling frequency varied with staffing, supplies, and observed virus activity. During initial months and periods of low activity, sampling occurred 1–3 times per week (mean 1.7 times/week for Oct 19, 2022–Jan 24, 2023, and Jun 28–Sep 19, 2023). During higher-activity intervals sampling increased to 3–5 times per week (mean 4.7 times/week for Jan 25–Jun 27, 2023, and Sep 20, 2023–May 31, 2024). Moore swabs were generally retrieved 24 hours after placement; swabs set on Fridays were collected Monday, yielding 72-hour exposure for those samples.
Wastewater samples were analyzed on-site using a clinical real-time PCR platform: the Cepheid GeneXpert Xpress system with Xpert Xpress CoV-2/Flu/RSV plus cartridges. The cartridges test for SARS-CoV-2, influenza A and B, and RSV and report cycle threshold (Ct) values. For surveillance, investigators added 300 µL of unconcentrated wastewater into each GeneXpert cartridge and followed the manufacturer’s instructions for clinical specimens. A concentration step was evaluated in samples collected through May 31, 2023, but was not adopted for routine surveillance because it required additional resources and time without notable improvement in virus detection. The local laboratory did not perform an internal validation of the GeneXpert method for wastewater, though prior work cited from the Public Health Agency of Canada validated similar clinical-platform use for wastewater analysis.
Clinical respiratory virus testing followed Yukon-Kuskokwim Health Corporation (YKHC) standards of care. Patients presenting with respiratory symptoms in ambulatory, emergency, or inpatient settings at YK Delta Regional Hospital were tested using midturbinate nasal swabs. Clinical samples were analyzed in the hospital laboratory using the Cepheid GeneXpert respiratory panel kit to detect SARS-CoV-2, influenza A and B, and RSV. The study used deidentified clinical testing data extracted from the YKHC electronic health record system. In addition to laboratory-confirmed tests, investigators performed a separate correlational analysis that included self-reported SARS-CoV-2 test results reported to YKHC public health during the study period.
Across 318 wastewater samples collected during October 2022–May 2024, the study detected SARS-CoV-2 in 265 samples (83.3%), influenza A virus in 128 samples (40.3%), RSV in 78 samples (24.5%), and influenza B virus in 29 samples (9.1%). Clinical testing volume for the same interval totaled 7,392 tests.
Investigators calculated Spearman correlation coefficients comparing wastewater signals with clinical results. Correlation values reported were: influenza B ρ = 0.85, influenza A ρ = 0.62, RSV ρ = 0.60, and SARS-CoV-2 ρ = 0.59. These correlations indicate that wastewater viral signals broadly tracked community clinical testing trends for the pathogens included in the surveillance panel. The wastewater results provided corroborating information that was used by public health teams to inform the timing of seasonal respiratory virus immunization campaigns in the region.
The project demonstrates that localized WS is operationally feasible in a remote, resource-constrained setting when using a compact clinical PCR platform and passive sampling. Key facilitators included selecting a sampling site that captured the majority of piped wastewater and a subset of hauled sewage, and conducting on-site testing to reduce logistical burdens associated with shipping samples to distant laboratories.
The team identified barriers that commonly limit WS adoption in rural communities—limited laboratory access, costs, staffing constraints, decentralized or non-piped systems, and competing priorities. The study’s choice to omit a concentration step for routine surveillance reflected a pragmatic balance between resource use and incremental gains in detection for their operational context.
Limitations noted in the study context include that the local laboratory did not validate the GeneXpert method specifically for wastewater and that sampled wastewater represents a mix of piped and hauled contributions that may influence signal strength. The report does not provide additional detail on temporal lags, Ct value distributions, or pathogen-specific detection limits in this summary; those details may be reported in the study appendix or full article.
In this remote Alaskan community, on-site wastewater surveillance using passive Moore swabs and a clinical PCR platform detected SARS-CoV-2, influenza A and B, and RSV and produced signals that correlated with clinical testing. The approach proved feasible for routine surveillance and supplied corroborative data that informed immunization campaign timing. The study supports the potential utility of locally implemented WS to augment public health surveillance in rural and remote settings, while noting operational trade-offs and the need for method validation in wastewater-specific contexts.