Officials are racing to conduct more testing to better understand the spread of the virus and its potential risk to humans.

With news Thursday night that a fifth of the U.S. milk supply contains fragments of bird flu virus, the Biden administration and dairy industry are racing to convince the public not to worry about the spread of the disease among the nation’s cattle.

Despite the assurances, the Food and Drug Administration’s announcement that 1 in 5 retail milk samples tested positive for viral fragments suggests that the virus may have spread beyond symptomatic dairy herds. The pathogen has now been found in at least 33 dairy herds across eight states since first being detected among Texas cattle in late March. Virologists say it could be much more widespread than that data suggests. To date, however, just one person has been confirmed to have contracted the virus — a dairy worker in Texas who developed a case of conjunctivitis, i.e. pink eye.

Federal officials and industry executives maintain the discovery of inactive fragments of the virus strain, known as H5N1, in milk sold to consumers is not, in and of itself, worrisome — rather, it’s evidence that the pasteurization process is working to neutralize the virus. But given that bird flu has never before spread to cattle, public health officials warn there are still many unknowns. And they and some farmers and lawmakers are now urging the government to rapidly expand its testing and research — and to make that data available ASAP.