Peering into wastewater for public health has a history dating back at least to the late 19th century, when a biologist in Boston cultured sewage in beef jelly, bouillon, boiled potatoes, and milk to see if anything would grow. Later, scientists in Scotland looked at wastewater to assess the spread of typhoid. After injecting monkeys with sewage in the 1930s, American researchers realized that wastewater polio virus concentrations correlated with community infections. It was the COVID-19 pandemic, however, that led to skyrocketing investment in wastewater disease surveillance in the United States—this time with the aid of modern biotechnology and without bouillon or monkeys.

As COVID transitioned from a deadly novelty to something closer to a mundane nuisance, testing for the virus fell off a cliff. Wastewater surveillance became central to public health officials’ ability to track COVID. The same is true for other threats, like H5N1 avian influenza. Bird flu has now spread from wild birds, to poultry, to cattle, and, worryingly, to a wide variety of other mammals, including people. Still testing remains limited. The federal government has invested at least $500 million in building wastewater-surveillance capacity since 2021. But that funding expires in September. Jennifer Nuzzo, an epidemiologist who is the director of The Brown University Pandemic Center, told me we may soon be left with an even murkier understanding of how diseases like COVID and bird flu are spreading.

Egg prices have risen 50% since March 2024, the result of an ongoing bird flu crisis that has both producers and consumers grappling for solutions. According to the U.S. Department of Agriculture, 166 million chickens have been infected and killed in the past three years, which means there are fewer egg-laying chickens, reduced supply, and higher prices. Mandatory culling, inadequate government reimbursement, and prevention costs have led to $1.4 billion in losses for the poultry industry, hurting both farmers and everyday Americans. But despite these soaring costs, the U.S. is about to sunset a relatively affordable, very effective tool we have for stopping bird flu — and other deadly viruses.

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This Pandemic Center-authored brief explores the current landscape of wastewater surveillance in the US and the importance of developing it further.