It emerged as a powerful tool for public health officials during the COVID-19 pandemic, when it was used to measure the prevalence of the coronavirus in communities across the country.
But wastewater surveillance (testing of wastewater for signs of pathogens such as SARS-CoV-2, poliovirus and mpox virus) has not yet been used to monitor the H5N1 bird flu virus.
Now, as officials try to determine the extent of bird flu outbreaks among dairy herds, some experts are urging that wastewater surveillance begin immediately. Others blame the U.S. Centers for Disease Control and Prevention for discouraging its use.
“Wastewater surveillance has consistently been shown to only improve upon, and often outperform, traditional surveillance when it comes to early/timely detection of outbreaks or surges,” said Denis Nash, distinguished professor of epidemiology and executive director of the Institute of Studies from the City University of New York. Implementation science in population health.
“In this case, since traditional surveillance doesn't really happen systematically, and wastewater surveillance is relatively cheap and easy to implement, it makes a lot of sense to me to go ahead and implement it strategically,” said Nash, whose lab developed Surveillance. New York City wastewater community for SARS-CoV-2.
However, that has not been the CDC's view.
Recently, Marc Johnson, a professor of molecular microbiology and immunology at the University of Missouri, said the agency told him not to use a virus assay it had created in order to track H5N1 outbreaks. The reason? Johnson said officials told him that would only add to the confusion.
Johnson said that if the trial had been used widely earlier this year, the spread of bird flu through the country's dairy herds could possibly have been stopped, or at least slowed.
“I always think the more information we have, the better,” he said.
However, he said he understood the government's reasoning.
“Public health doesn't like ambiguous information,” he said. “If you get a positive result, you don't know if it's from a cow or a bird. Or maybe from the milk thrown down the drain.”
The CDC did not respond to questions from the Times.
Concern about the virus increased in March, when federal officials announced the discovery of bird flu in a Texas dairy herd. Over the next few weeks, reports of the virus began to appear in other states. It also appeared in barn cats drinking raw milk and in a dairy worker.
H5N1 bird flu has already been detected in 36 herds in nine states, and health and USDA officials are struggling to determine its extent. They believe the virus was introduced by a wild bird, either through contact or food, on a Texas farm in December, giving the virus months to travel to other flocks and animals.
The virus was also found in one of five supermarket milk samples tested by federal investigators. Those samples showed that the virus had been inactivated through pasteurization, reducing the threat to people's health.
In California, where the virus has not yet been detected in dairy cows, wildlife officials are cautiously monitoring populations of migratory wild birds, as well as domestic poultry and farm animals.
Eric Topol, a professor of molecular medicine at the Scripps Research Institute in La Jolla, said the CDC is “off the mark” in saying wastewater monitoring would cause confusion.
“If anything, we need to track the spread of the virus and its evolution, something the USDA and CDC are not doing well,” he said.
Michael Payne, a dairy educator and researcher at the University of California School of Veterinary Medicine, agreed with that sentiment. Although he was not familiar with the assay Johnson devised, he said an accurate test would be valuable.
“Such a wastewater analysis could be a useful tool, even given the uncertainty about the exact origin of the virus,” he said. “There is a growing literature using PCR testing in wastewater to measure pathogens of public health concern.”
CUNY's Nash said he would advocate for a “strategic deployment of community-based and facility-based wastewater surveillance.”
He said testing wastewater at hospitals and health clinics would provide clear signals if an outbreak occurred. Starting testing now, when a baseline can be established for other “confusing” elements such as contaminated milk and bird droppings, would help quiet that noise.
He said that in the current situation, “we need reliable early warning because if community spread were to occur, each additional day of warning would be very important in terms of potential lives saved.”
