The detection of bird flu virus this week in a batch of unpasteurized milk sold in California underscores what health experts say are the known and potential risks of the products.

Scientists are warning about the continued transmission of dangerous H5N1 bird flu, saying that the virus is more widespread than believed.

Bird flu can also cause respiratory and classic flu-like symptoms, including cough, runny nose, fever, sore throat, body aches, headaches, fatigue, shortness of breath, and pneumonia, the CDC says. Some people in the U.S. who have caught bird flu have experienced respiratory symptoms as well.