Wastewater shows how COVID-19 is spreading in Idaho communities

August 23, 2022
Dr. Christopher Ball, Idaho Bureau of Laboratories chief

Idaho is publishing COVID-19 data from samples collected at participating wastewater treatment facilities around the state. The Wastewater testing tab on the state’s COVID-19 case, laboratory, and hospital data dashboard.  Click “Wastewater Testing” at the  dashboard to see a clickable map, that lists participating locations, and clearly-illustrated trends.

People infected with the virus that causes COVID-19 often shed the virus in their feces, even if they don’t have symptoms. The virus is detectable in wastewater, which allows wastewater surveillance to serve as another way to monitor how COVID-19 is spreading in a community.

In Idaho, wastewater surveillance is becoming an important tool for monitoring COVID-19. Samples are collected by participating wastewater treatment facilities two or three times per week and sent to one of five testing laboratories at Idaho-based universities and the Idaho Bureau of Laboratories. Testing done at the laboratories determines the concentration of the virus that causes COVID-19 in the wastewater samples.

Viral concentration data is uploaded to the Centers for Disease Control and Prevention’s (CDC’s) National Wastewater Surveillance System, where it’s aggregated and analyzed with data from similar programs across the U.S. The Idaho data is then pulled from the CDC’s central database and published on the state’s dashboard.

Wastewater system trends are estimated by analyzing recent concentrations obtained for individual wastewater facilities. If a statistically significant trend is identified for a given site, the treatment site is noted as an increase or decrease. If no significant trend can be identified levels of virus in samples from that treatment site are considered to be stable.

Challenges remain as this new program expands in the state. Participation in wastewater monitoring is voluntary for all contributing treatment facilities, and occasionally sampling may be missed or delayed at either the sampling or testing locations. This is especially true when staffing is strained as can happen when COVID-19 cases are rapidly increasing.

New sites are regularly being added to the network. Trends from new test sites are expected to swing wildly at first but then stabilize over time as additional data are added.

There are hundreds of wastewater treatment facilities in Idaho. Capacity is not yet large enough to sample and test wastewater from all facilities, so sites have been prioritized based on the size of the population served, the location of the facility, and the facility’s ability to collect and submit samples using standardized techniques.  Currently, we have contributing facilities from each region in Idaho, which will help us continue to monitor how COVID-19 is spreading.

Dr. Christopher Ball is the laboratory bureau chief for the Division of Public Health, Bureau of Laboratories, where he serves as the laboratory director and clinical consultant. Dr. Ball is certified in molecular diagnostics by the American Board of Bioanalysis and serves as co-chair of the Governor’s Coronavirus Testing Task Force. Since February 2020, he has been focusing on providing testing, developing guidance, and expanding testing capacity to support Idaho’s response to the coronavirus pandemic.



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The Idaho Department of Health and Welfare is dedicated to strengthening the health, safety, and independence of Idahoans. Learn more at healthandwelfare.idaho.gov. 

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