The Centers for Disease Control and Prevention (CDC) has unveiled a new influenza A wastewater tracker as part of its efforts to monitor the spread of H5N1 avian influenza. This comes as three states in the US reported an increase in detections of the virus in dairy herds.

Recent developments have indicated the possibility of dairy cows asymptomatically spreading H5N1. However, testing in dairy herds has been inconsistent, with delays in reporting. In order to gain better visibility into the spread of the virus, virologists and public health officials are exploring alternative methods, including wastewater testing.

The CDC has launched an influenza A wastewater dashboard on its H5N1 monitoring page. It should be noted that the current wastewater monitoring, conducted through the National Wastewater Surveillance System, does not distinguish the specific subtype of influenza A or determine the source of the virus. Influenza viruses can originate from humans, animals, or contaminated products such as milk.

The interactive map provided on the CDC's dashboard categorizes current influenza A levels compared to the levels observed during the 2023-2024 season. When the levels reach the 80th percentile or higher, the CDC partners with state and local authorities to investigate contributing factors.

Over the past two weeks, 230 sites from 34 states met the criteria for data reporting. Among them, three sites in three states: Saline County, Kansas; Pinellas County, Florida; and Kane County, Illinois, reported high levels of influenza A. The CDC is closely monitoring these areas and working with relevant authorities to better understand the factors driving the high levels.

Experts in the field have expressed their support for the CDC's wastewater dashboard. Dr. Marc Johnson, a virologist at the University of Missouri, commended the CDC for sharing the information, suggesting that samples showing suspiciously high levels should be tested for the H5 subtype. Similarly, Dr. Brian Wasik, a molecular biologist at Cornell University, believes that the dashboard will provide valuable insights into baseline levels and longitudinal trends, helping identify further areas of focus.

In related news, the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) has reported four additional detections of H5N1 in dairy herds, bringing the total number to 46. These detections have occurred in states where cases were already identified, including two in Michigan, one in Texas, and one in Idaho.

Furthermore, APHIS has recorded three more H5N1 detections in wild birds, with two of them coming from counties where affected dairy herds were found. The detections involved a rock dove from Michigan's Ionia County, a black-billed magpie from Idaho's Cassia County, and a red-tailed hawk found dead in Dutchess County, New York. All of these detections have been confirmed to involve the Eurasian H5N1 subtype.

As the number of cases continues to rise, monitoring and surveillance efforts by the CDC and USDA are crucial in detecting and containing the spread of H5N1 avian influenza. The introduction of the influenza A wastewater tracker will provide valuable data to guide public health interventions and prevent further outbreaks.