The FDA reported Tuesday that it had identified viral fragments of H5N1 avian flu in milk purchased at retail outlets, though it maintains the milk is still deemed safe for consumption.
In an update on the ongoing bird flu outbreak in cattle, the FDA indicated the viral remnants were likely detected through sensitive lab tests and are likely residuals of viruses neutralized during pasteurization. The agency expressed skepticism that these remnants could infect humans but is conducting further tests to confirm.
The FDA described these egg inoculation tests as the "gold standard" for ascertaining viral viability and human infectivity.
"To date, there is no evidence altering our assessment that the commercial milk supply is safe. Findings from various studies will be disclosed in the coming days to weeks," the FDA stated.
Dr. Eric Topol, founder of the Scripps Research Translational Institute, suggested the presence of viral fragments in milk suggests a broader spread of the outbreak.
"The dissemination to cows appears more extensive than previously understood," Topol noted in a Tuesday email.
While the USDA confirmed highly pathogenic avian flu in dairy cows in late March, it marks the first instance of this virus in cattle. Infected cows have since been found in over 30 farms across eight states. Concerns have been raised regarding the USDA's limited information sharing about the virus and its slow pace.
The FDA noted Tuesday that milk from sick cows is being diverted or destroyed, while milk sold across state lines undergoes pasteurization to eliminate microbes. Despite the detection of virus in raw milk, pasteurization is generally expected to mitigate pathogens to a level posing no health risk, the FDA assured.
The FDA underscored that 99% of commercial milk comes from farms adhering to pasteurization protocols, albeit noting pasteurization doesn't render milk completely sterile.
Consequently, the FDA has been testing milk samples from grocery stores nationwide, collaborating with the CDC's food safety team.
Efforts to track the outbreak have depended on voluntary reporting, as reporting avian influenza in cattle is not mandatory.
"No one anticipated its presence in cows," said Dr. Richard Webby, WHO's coordinator for influenza ecology studies.
Dr. Michael Osterholm expressed concerns about the potential spread to pigs, emphasizing the need for proactive reporting in all livestock.
Currently, the CDC monitors emergency department and flu testing data in areas where H5N1 has been found in dairy cattle for any unusual trends, with no abnormal activity reported thus far.
CDC spokesperson Jason McDonald confirmed 23 individuals with H5N1 exposure have been tested, with only one positive case reported in Texas.
