Bird Flu's Genes Lurk in Wastewater

Scientists tested wastewater treatment plants in three locations for the H5 marker to track the prevalence of typical viruses and H5N1.

Wastewater testing to detect viral activity levels of influenza, COVID-19, and other pathogens can help health officials track the spread of these diseases. However, testing wastewater for bird flu may be more challenging as tests would have to differentiate between more prevalent flu viruses and H5N1.

In a study published as a preprint on the medRxiv server, which has yet to be peer-reviewed, scientists from Stanford, Emory, and Verily Life Sciences developed a test to distinguish between typical flu viruses and H5N1. This spring, the researchers, who are affiliated with the WastewaterSCAN network, tested samples for the H5 subtype.

In plants located in areas with high H5N1 activity among dairy cattle, the scientists found that as influenza A viral concentrations rose, so did H5N1 markers. Moreover, H5N1 gene levels were close to influenza A concentrations, which may indicate that a significant percentage of viruses found in samples were H5 subtypes.

In one wastewater treatment facility in Texas, an area with confirmed cases of bird flu in cattle, influenza A levels were some of the highest ever measured.

The testing shows that viral surveillance via wastewater systems can track the spread of potentially concerning viruses infecting animals.

"Our findings demonstrate wastewater monitoring can detect animal-associated influenza contributions and highlight the need to consider industrial and agricultural inputs into wastewater," the study's authors wrote. "This work illustrates the value of wastewater monitoring for comprehensive influenza surveillance for diseases with zoonotic potential across human and animal populations."

The latest update on bird flu in cattle

Over 35 dairy cattle herds in nine states have been stricken with the highly pathogenic H5N1 bird flu virus. The confirmed cases among cattle have sparked concern about the potential for the virus to mutate and spread between people.

So far, only two individuals have become infected after exposure to poultry or cattle, and no cases of human-to-human transmission have been reported.

Recently, health officials detected H5N1 viral fragments in store-bought pasteurized milk samples. The U.S. Food and Drug Administration (FDA) says these fragments pose no risk to humans. However, health officials conducted testing to determine if infectious forms of the virus are present in milk.

The FDA posted an H5N1 update on May 1, saying it did not detect any live, infectious virus in pasteurized commercial milk products, including cottage cheese and sour cream. The agency's testing also found no viral fragments or intact viruses in powdered infant formula products.

On April 30, the U.S. Department of Agriculture (USDA) said it would test ground beef for H5N1 fragments but is confident the United States meat supply is safe.

On May 1, the FDA, the CDC, and the U.S. Department of Agriculture held a joint press conference and announced that pasteurized dairy products like cottage cheese, sour cream, and powdered infant formula did not contain a virus.

Dr. Donald Prater, acting director of the Center for Food Safety and Applied Nutrition for the FDA, said, "These samples underwent acute qPCR (quantitative polymerase chain reaction) testing, as well as the same egg inoculation test, and we're encouraged that this preliminary testing also did not detect any viable virus."