As the Centers for Disease Control and Prevention (CDC) explains, bird flu is a disease caused by the influenza A virus. At the same time, recent CDC data shows that seasonal influenza A is rising across the U.

CDC officials say they extended the guidance now because they are seeing more H5N1 patients whose illness they cannot track back to an infected bird or cow.

NBC News Medical Contributor Dr. Kavita Patel speaks with Gadi Schwartz about the difference in symptoms between a cold and the flu and explains the CDC's urge for faster testing to find human bird flu cases.