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Samples from wastewater plants can help predict COVID-19 trends, according to The Wall Street Journal (subscription).

The benefits: Wastewater testing can help identify virus surges and circulating variants before testing and case data. Wastewater testing is helpful largely because it is a low-cost technique that covers a massive data source. Health officials believe it will serve as an important early-warning tool going forward, especially as testing sites and data reporting efforts are being scaled back in many states.

The flaws: In some places, wastewater monitoring is not effective. Federal officials estimate that about one in five American households, usually located in more rural areas, use septic systems that don’t feed into wastewater plants.

CDC leading the way: “ The CDC established a wastewater surveillance network in late 2020 and added wastewater data to its public Covid-19 dashboard in February. The system currently includes data from more than 700 sampling sites that cover roughly one-quarter of the U.S. population. The agency has a contract with a testing company to provide twice-weekly testing to more sites and is aiming to expand its network into all 50 states within the next few years.”

Data collection difficulties: Right now, comparing and understanding data from different wastewater sites can be difficult because of differing frequencies and analytical approaches. The CDC is working on ways to standardize and simplify its data.

Local success: In Boston, data from wastewater samples clearly predicted the rise and fall of the omicron wave and was used by public health officials to make effective decisions on increasing and decreasing COVID-19 restrictions.

National results: “The number of wastewater sites indicating virus increases on a Centers for Disease Control and Prevention dashboard has risen in recent weeks, though the majority of sites still show declining levels.”