Avian influenza detected in Arizona county wastewater sampling sites
Risk to the general population remains low
6 January 2025
3 minute read
By: As part of routine wastewater surveillance in Maricopa County in Arizona, Maricopa County Department of Public Health (MCDPH) reported the detection of an influenza subtype associated with avian influenza in local wastewater. No human cases of avian flu have been detected in Maricopa County, and the risk to the general population remains low.
Wastewater monitoring is a tool used to detect genetic material from microbes, like influenza A and its subtypes, in untreated wastewater, helping inform public health and partners on changing disease activity. The influenza A(H5) subtype, which can include H5N1 that is associated with avian influenza (also known as bird flu), was detected by all three cities within Maricopa County that conduct wastewater monitoring—Phoenix, Surprise, and Tempe—but it is not currently possible to confirm a precise source location of the viral detection.
Avian influenza has been detected in Arizona, including a commercial poultry farm in Pinal County, and a backyard flock and animals at a zoo in Maricopa County. The H5N1 detections in Pinal and Maricopa counties where further genomic testing was done are the same strain of H5N1 that is occurring in wild birds. Tests with other samples are pending. The same strain-specific testing in wastewater samples is not available so this link cannot be confirmed. There have been no detections of H5N1 in dairy cattle in Arizona.
“Wastewater monitoring is one of multiple tools we have to proactively monitor for avian flu in our community,” said Nick Staab, assistant medical director at MCDPH. “Given that no human cases have been identified in Maricopa County through our other disease detection methods and there is no recent documented spread of H5N1 influenza from human to human, the overall risk of avian flu to people remains low.”
Avian influenza is most often seen in wild and domestic birds; human cases have been rare and primarily in people with close, unprotected contact with sick or dead animals, their bedding, or their droppings. While wastewater monitoring may provide limited details, it provides important information about the presence of the H5 subtype, so that people can take appropriate precautions. This includes avoiding contact with sick or dead birds and wearing appropriate protective gear when handling sick or dead animals, their droppings, or their bedding. It is also advised to avoid consuming unpasteurized (raw) dairy products. Pasteurization kills viruses, including H5 influenza strains, that could come from infected dairy cows.
There is currently an increase in seasonal respiratory viruses, such as COVID-19 and seasonal flu strains, making it more likely that people in the community will come into contact with those viruses than avian flu. “To prevent illness, we want residents and visitors to focus on taking general respiratory virus prevention measures,” said Staab.
