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Volume 32, Supplement –Summer 2026
SUPPLEMENT ISSUE
Other
Progress and Expansion of the National Wastewater Surveillance System, United States, 2020–2024
, Megan Bias1, Stacie Reckling, Kaniz Madhobi, Daniel Cornforth, Igor Volkov, Andrew L. Rainey, Benjamin Lorentz, Kaitlin R. Taibl, Lisa P. Oakley, Rachel West, Rory Welsh, Jeffrey W. Mercante, Niketta Womack, Nicole Fehrenbach, and Jonathan Yoder
Table 1
Characteristics of sites participating in the National Wastewater Surveillance System, United States, 2023, 2024, and 2020–2024*
| Characteristics | 2023 | 2024 | 2020–2024 |
|---|---|---|---|
| States and territories, no. |
53 |
52 |
53 |
| Counties, no.† |
1,030 |
990 |
1,180 |
| County RUCC, by population, no. (%)‡ | |||
| Metropolitan | |||
| >1 million | 274 (27) | 245 (25) | 280 (24) |
| 250,000–1 million | 187 (18) | 197 (20) | 214 (18) |
| <250,000 | 156 (15) | 155 (16) | 175 (15) |
| Nonmetropolitan | |||
| Adjacent to metro area >20,000 | 102 (10) | 105 (11) | 119 (10) |
| Not adjacent to metro area >20,000 | 39 (4) | 30 (3) | 45 (4) |
| Adjacent to metro area 5,000–20,000 | 94 (9) | 94 (10) | 119 (10) |
| Not adjacent to metro area 5,000-20,000 | 78 (8) | 75 (8) | 96 (8) |
| Adjacent to metro area <5,000 | 45 (4) | 42 (4) | 62 (5) |
| Not adjacent to metro area <5,000 |
54 (5) |
47 (5) |
70 (6) |
| Sites by US Census region, no.§ | |||
| Midwest | 705 | 662 | 829 |
| Northeast | 376 | 340 | 404 |
| South | 480 | 509 | 642 |
| West |
393 |
356 |
443 |
| Site population | |||
| Persons served by all sites, no. (% of US population), in millions¶ | 163 (49) | 150 (45) | 178 (54) |
| Persons served per site, median (IQR), in thousands |
24 (8–77) |
24 (8–75) |
21 (7–67) |
| Site characteristics | |||
| Sites, no. | 1,967 | 1,871 | 2,331 |
| Tribal land sites, no. | 7 | 8 | 14 |
| Site location | |||
| WWTP | 1,672 | 1,605 | 1,988 |
| Upstream | 295 | 266 | 343 |
| Targets tested for at site, no.# | |||
| SARS-CoV-2 | 1,952 | 1,847 | 2,308 |
| Monkeypox virus | 650 | 481 | 731 |
| Influenza A | 870 | 1,301 | 1,364 |
| Influenza A(H5) | 25 | 551 | 551 |
| Respiratory syncytial virus | 723 | 1,215 | 1,256 |
| Site management, no. (%)** | |||
| Local health department | 63 (3) | 62 (3) | 63 (2) |
| State health department | 1,523 (77) | 1,551 (83) | 1,853 (79) |
| Commercial national contractor | 397 (20) | 188 (10) | 493 (21) |
| Academic partner program | 198 (10) | 192 (10) | 199 (9) |
| Laboratories testing samples from sites, no. | 95 | 102 | 139 |
| No. samples collected per site per week, median (IQR)†† | 2 (1–2) | 2 (1–2) | 2 (1–2) |
| Automated concentration data submission, sites (health departments), no. | 312 (5) | 452 (10) | 469 (10) |
| Sewershed boundaries, no. (%)‡‡ | 1,224 (77) | 1,233 (82) | 1,407 (73) |
*IQR, interquartile range; RUCC, Rural-Urban Continuum Code; WWTP, wastewater treatment plant. †Counties were included as long as a wastewater site served some part of the county. ‡By 2023 RUCC (https://www.ers.usda.gov/data-products/rural-urban-continuum-codes). §Some sites are not part of a US Census Region. ¶The US Census Bureau population estimate of 331,449,281 persons (as of April 1, 2020) was used to estimate percent of the US population covered by wastewater sampling sites. That number represents the sum of population served by WWTP sampling locations. Wastewater sewersheds may serve overlapping populations. #Sites may be testing for >1 target; the numbers of sites testing for each target in the table are not mutually exclusive. **Sites may be managed by >1 entity; the numbers of sites managed by each entity in the table are not mutually exclusive. Wastewater data from health departments may reflect testing from public health, commercial, and academic laboratories. ††All samples collected at a site were included in the median of number of samples collected per week regardless of site management. ‡‡Sewershed boundaries are submitted for sites located at a WWTP managed by local or state health departments or the commercial contractor.
1These first authors contributed equally to this article.