LLess than a month ago, researchers first reported the possibility of testing wastewater for signs of the H5 influenza virus that is currently sickening dairy cows in at least nine states. -United. This technology is now on the threshold of real-world use.
WastewaterSCAN, an infectious disease tracking wastewater surveillance network led by Stanford University and Emory University in partnership with Verily Life Sciences, has begun expanding H5-specific testing on samples from across the of its 190 locations at processing plants in 36 states. The philanthropically funded effort will begin sharing data with local public health officials and on its public dashboard in the coming weeks, one of its leaders told STAT.
Faced with the dairy industry’s widespread reluctance to test cows or the farmworkers who care for them, scientists and public health officials trying to assess whether the spread of the disease is speeding up or slowing down are largely in ignorance. Testing wastewater for a genetic signature of the H5N1 avian flu virus could give communities another way to spot potential outbreaks.
“It’s a very new thing that avian flu is circulating among dairy cattle and we still have a lot to learn,” said Marlene Wolfe, an environmental microbiologist and epidemiologist at Emory and one of the directors of WastewaterSCAN. “We’ve heard that more information would be helpful and that this is an additional piece of information that can help authorities understand what might be happening with these outbreaks.”
About a year ago, the WastewaterSCAN team developed a probe that detects H5 influenza viruses, including the H5N1 virus that has now been found in 52 dairy herds in nine states. The test sat unused until this spring, when unusually high influenza A activity began to light up their dashboard in the Texas panhandle – the same region where the first cases of H5N1 in dairy cattle were confirmed on March 25.
Wolfe and his colleagues went back and applied the probe to samples collected from three wastewater treatment plants in the region and found that the spikes were mainly due to large amounts of viral fragments from the specific H5 influenza.
The WastewaterSCAN team hypothesized that these viral fragments resulted from releases from dairy processing plants in the region. But there is currently no effective way to determine the exact source of viral contamination in a given sewage basin: in addition to human sewage, animal products can also end up there, either through agricultural spills and industrial, or by environmental runoff.
Their results, which were released as preprint in April, were published Monday in Environmental Science & Technology Letters. So far, the scientific literature on the detection of H5 influenza virus subtypes in wastewater is sparse but encouraging. In another recent pre-publication study, researchers from the University of Texas and Baylor University began discovering H5N1 sequences in wastewater treated at 19 plants across nine Texas cities starting March 4 this year. year.
Wastewater epidemiology has been used for decades to detect polio in countries where the disease remains endemic and, more recently, to estimate the prevalence of opioid use in U.S. communities. But national wastewater monitoring capacity has been significantly strengthened during the Covid-19 pandemic, gaining visibility and credibility as an effective pandemic management tool. In addition to academic research efforts like WastewaterSCAN, the Centers for Disease Control and Prevention operates the National Wastewater Surveillance System, which monitors 600 sites for SARS-CoV-2, mpox, and influenza A.
Earlier this month, the CDC began publishing data from its influenza A tracking efforts on a public dashboard. Since the agency is not conducting H5-specific testing at this time, the dashboard only shows overall influenza A activity. But like other influenza A viruses that cause human illness, they tend to circulate at very low levels during the summer months in the United States, the presence of high levels of influenza A virus in wastewater could be a reliable indicator that something unusual is happening – at least until the return of higher levels of seasonal flu in the fall.
In its interactive map, the CDC presents current influenza A levels compared to historical data, providing the context needed to determine if what is being observed is abnormal. When levels reach the 80th percentile or higher, officials said the agency works with state and local partners to investigate further. For now, the CDC is only including data from wastewater treatment sites that were collecting samples during last year’s flu season, starting October 1, 2023. There are currently 230 sites across 34 states that meet these criteria.
Tom Skinner, a CDC spokesperson, told STAT by email that the agency is in communication with WastewaterSCAN and other academic groups to better understand the potential value of more widespread testing for H5-specific subtypes.
“CDC is considering the possible role of other sites for testing influenza A virus subtype H5 in wastewater with our public health partners,” he wrote. “Wastewater monitoring is an evolving science. We continue to examine data and methodologies that can improve our public health surveillance.
Wolfe agrees that there is still much to learn in the field of wastewater epidemiology about how to interpret the type of H5-specific data that WastewaterSCAN will soon collect. But it’s this particular data that local public health officials are currently hungry for, she said. “If there is an increase in the number of influenza A cases – because this is data that a lot of people have access to – is it really due to an H5 virus or not? Being able to disambiguate and understand where these signals are coming from is something that there is a lot of interest in.
Wastewater isn’t the only workaround researchers are using to try to track the spread of H5N1. Frustrated by the lack of testing and limited genetic data shared by the U.S. Department of Agriculture, some scientists have begun sequencing the avian flu virus from store-bought milk to monitor its movements and research any changes in its genome that might make it more capable of infecting humans.
Michigan public health officials on Wednesday confirmed a second human case of avian flu infection linked to the current outbreak in dairy cows. The farmworker had only mild symptoms and has since recovered, and authorities have stressed that the risk to the public from H5N1 remains low. But influenza viruses are known for their evolutionary capacity, and if this becomes endemic in dairy cows, it would increase the potential risks to humans.