More than a dozen cats have been killed or sickened by bird flu that is spreading in raw food products, the Food and Drug Administration says, prompting a federal probe into how the virus got into the pet food supply chain.

Denver health officials are once again reminding people to steer clear of sickly or dead fowl due to increasing attention in national media of highly pathogenic avian influenza.

A Mercer County farm worker came into contact with dead poultry that was infected with the disease, the state's health department reports.