Scientists were slow to recognize that Covid spreads through the air. Some are now trying to get ahead of the bird flu.

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.

When it comes to the potential of H5N1 avian flu, otherwise known as bird flu, picking up mutations that might lead to human-to-human spread, that "train has already left the station," warns one ...