There have been sixteen human bird flu cases in the United States this year, including the two in California. Fifteen of those cases were in farm workers at infected poultry or dairy farms. Public health officials say the risk to the general public from bird flu is low.

The sick workers had conjunctivitis (pink eye) and did not report respiratory symptoms, Nirav Shah, principal deputy director at CDC, said.

More than 250 dairy herds in 14 states have tested positive for bird flu this year. Fifty-six have been in California, according to the U.S. Department of Agriculture.