New bird flu strain detected on poultry farm as experts monitor mutations

CDC warns bird flu virus showing mutations in severe cases

Fox News senior medical analyst Dr. Marc Siegel explains what's behind human cases of bird flu in U.S.

A new strain of bird flu (highly pathogenic avian influenza, or HPAI) has been detected on a duck farm in California. (iStock)

"Birds are very susceptible to avian influenza in general. Some strains of the virus are mild, some deadly," an expert told Fox News Digital. (iStock)

There are "continual mutations" of flu strains, so not all H1 versions are the same, a doctor said. (iStock)

Researchers become concerned when there are large outbreaks of bird flu in poultry farms, one expert noted. (iStock)

To date, there have been 67 confirmed cases of human bird flu in the U.S. and one death, according to the CDC. (iStock)