Viral Surge In CA Wastewater Raises Alarms: If Not Flu, Then What?

"This virus has the potential to seriously disrupt our agricultural supplies and also jump from other mammals to humans and become an epidemic or even a pandemic," Dr. Michele Barry of the Stanford Center for Innovation in Global Health told Stanford Medicine, a university publication.

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Millions of poultry birds in 48 states - including California - have been sickened by H5N1 since 2022. It was first reported in cattle in March. Since then, outbreaks have spread to 46 dairy herds in nine states, according to U.S. Centers for Disease Control and Prevention data.

One farm worker became infected after being exposed to dairy cattle in Texas, the CDC said in April. The worker reported only eye redness as a symptom and has since recovered. Another person was infected with H5N1 in 2022 after being exposed to poultry, the agency said.

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Still, the CDC casts the possibility of a human outbreak of H5N1 as unlikely.

"CDC believes the current risk of A(H5N1) infection to the general public remains low," the agency said last week.

But some experts have raised concerns that regulators aren't watching H5N1 closely enough amid the spread to mammals, which has also proven to be fatal to dozens of other mammal species worldwide, the PBS NewsHour reported.

"What we have is a situation where the virus, in a sense, has more shots on goal to jump from a related species, a mammal like us. And now people are no doubt being exposed on a daily basis in pretty large numbers," Michael Worobey, an evolutionary biologist at the University of Arizona told PBS.

Stanford's Barry pointed out that there has been no evidence of human-to-human transmission. But scientists are lacking data in that area: She said in the case of the Texas dairy worker, researchers were unable to do testing that could help reveal how transmissible the virus might be to humans.

Some experts say more attention should be focused on wastewater, which is routinely tested to determine the levels of influenza A viruses in a community. That includes typical flu bugs that spread between people each winter, but it also includes H5N1, the Los Angeles Times reported.

Recent testing has shown a moderate-to-high upward trend in dozens of communities across California, including in the Bay Area and San Diego. That's unusual for this time of year - flu season has ended. The data doesn't necessarily mean that bird flu is present in local wastewater, but it does raise the concern, the Times reported.

And at this point, it's not possible to discern whether those pops of influenza A include H5N1. A number of experts are urging authorities to specifically test wastewater for bird flu in order to get a better understanding of the current state of the virus.

"We need to track the spread of the virus and its evolution, which isn't getting done well by USDA and CDC," Eric Topol, a professor of molecular medicine at Scripps Research Institute in La Jolla told the Times.

A California Department of Public Health spokesperson told Patch that officials have not recently seen an increase in human cases of influenza A and noted that bird flu has not been detected in dairy cattle, dairy products or humans in California to date.

"CDPH has been working with the Centers for Disease Control and Prevention, and local health departments, to monitor influenza A in wastewater and investigate increasing prevalence in wastewater that is not following human influenza trends. CDPH is working with these groups to investigate these increases, including testing specifically for H5 within wastewater," the spokesperson said.

"Local public health departments continue to review our wastewater data and trends in combination with other human influenza surveillance system data and collaborate with partners to better understand factors that could contribute to increases, such as animal sources located in individual sewer systems (e.g., livestock, wild birds or waste from a milk processing plant)."

The CDC recommends that people use masks and eye protection if they're exposed to animals who are sick or potentially sick with bird flu. They should also avoid eating uncooked or undercooked food products, as well as unpasteurized (raw) milk and cheeses.

Recent FDA testing found traces of the virus in 20 percent of retail milk samples, but authorities say pasteurization kills the virus.