First national look at H5N1 bird flu in wastewater suggests limited spread in US

Results from recent wastewater testing across the US suggest that H5N1 bird flu may not be as widespread as feared. The data showed detections of the H5 protein portion of the flu virus in sewage from 14 water treatment plants in five states. This suggests that the ongoing outbreak in dairy cattle may largely be confined to states that already have affected herds. The test for H5 was run in 190 monitoring sites across the US over the past two weeks. Nine states are not enrolled in the surveillance. There were detections in two states where no affected dairy herds have been identified, but both states have seen recent outbreaks of H5N1 in poultry. The sources of H5 in wastewater are not yet known. There’s a chance the detections might be due to human infections or other sources such as infected wild birds contaminating wastewater or stormwater runoff. The wastewater testing provides an additional tool to monitor the virus amid the outbreak. Testing of cattle has been limited, and many farmers have been reluctant to allow government officials into their farms for further surveillance. The CDC is monitoring for human infections and hopes to conduct an epidemiological study to better understand the risk of transmission between animals and humans on farms. It encouraged healthcare providers to remain vigilant for signs and symptoms of influenza virus infection and to forward positive influenza A specimens to public health laboratories for additional testing.