A version of the avian influenza virus different from the one rampaging through herds since last spring has been detected in dairy cows in Nevada, USDA says.

The finding indicates that the virus, known as H5N1, has spilled from birds into cows at least twice — leading to these two sets of infections — and that it could continue to do so. It also suggests that the virus may pose a persistent risk to cows and to the people who work closely with them.

Currently, there are a total of 67 confirmed human cases in the United States and one death associated with the bird flu.

In late January, scientists at the World Organization for Animal Health (WOAH) reported the first cases of H5N9 avian influenza in the U.S., on a duck farm in California. The latest strain isn’t a surprise,

Bird flu (H5N1) primarily affects birds but has spread to mammals, including humans. While human transmission remains rare, scientists fear mutation could make it airborne, potentially triggering a global health crisis.

This op-ed argues that to fight avian flu and other animal-borne illnesses, we need to overhaul our food system.