What you need to know about bird flu. Public health experts are closely watching avian influenza, which has affected chickens and cows and sickened some Americans.

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.

Researchers have stressed that bird flu still poses a minimal risk to the general public, though that may change as the virus continues to circulate and potentially mutate. But the many empty shelves in stores and higher prices on the eggs that people can find have raised concerns among consumers about the safety of the egg supply.

Dairy cows in Nevada have been infected with a new strain of bird flu, marking the second strain detected in herds since March.

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.

Bird flu is continuing to spread across the United States, infecting wild birds and backyard poultry. It's causing egg prices to soar and availability to plummet.

USDA Detects Bird Flu Strain in Dairy Cattle Not Previously Seen in Cows, According to Email Seen b By Leah Douglas (Reuters) - The U.S. Department of Agriculture has detected a bird flu strain in dairy cattle that previously had not been seen in cows,