Debate over Reliability of Wastewater Testing for H5N1 Bird Flu in U.S. Dairy Herds

Researchers are increasingly utilizing wastewater testing to monitor the spread of H5N1 bird flu among U.S. dairy herds. However, there are questions surrounding the reliability of these tests. The U.S. Centers for Disease Control and Prevention (CDC) maintains that current tests are standardized and effective. Yet, some researchers, such as Denis Nash from City University of New York, express concerns about the tests potentially missing certain virus subtypes like H5N1.

Wastewater testing for health surveillance significantly increased during the COVID-19 pandemic. Alexandria Boehm from Stanford University notes that this method has rapidly evolved, becoming a routine monitoring tool.

Since the bird flu was identified in Texas dairy cattle in late March, researchers have been analyzing wastewater samples using existing influenza A tests, which were primarily designed for human flu viruses. Debate continues over whether these tests can reliably detect H5N1. Marc Johnson from the University of Missouri suggests that most labs use broad panels capable of capturing multiple subtypes, including H5.

On Tuesday, the CDC released a dashboard showing influenza A detections at over 650 sites nationwide, with high levels reported only in Florida, Illinois, and Kansas. Jonathan Yoder of the CDC defended the standardization and broad scope of these tests, denying evidence of them missing bird flu.

Contrary findings came from a Texas research team, including scientists from Baylor College of Medicine and UTHealth Houston, who used hybrid-capture sequencing to identify high levels of H5N1 in wastewater from nine Texas cities. Their method differs from PCR testing by capturing a wider range of viruses, bolstering confidence in detecting H5N1 specifically.

While Texas researchers speculate on multiple sources of bird flu contamination, they have ruled out human transmission due to unique genomic markers absent in wastewater samples. The innovative approach demonstrates a potential new paradigm in metagenomic testing for public health surveillance.