Zeynep Tufekci: This may be our last chance to halt bird flu in humans and we’re blowing it

The outbreak of H5N1 avian influenza among U.S. dairy cows, first reported on March 25, has now spread to at least 33 herds in eight states. On Wednesday, genetic evidence of the virus turned up in commercially available milk. Federal authorities say the milk supply is safe, but this latest development raises troubling questions about how widespread the outbreak really is.

So far there is only one confirmed human case. Rick Bright, an expert on the H5N1 virus who served on President Joe Biden’s coronavirus advisory board, told me this is the crucial moment. “There’s a fine line between one person and 10 people with H5N1,” he said. “By the time we’ve detected 10, it’s probably too late” to contain.

That’s when I told him what I’d heard from Sid Miller, the Texas commissioner for agriculture. He said he strongly suspected that the outbreak dated back to at least February. The commissioner speculated th...