Free Antigenic drift and Antigenic shift Animation

When a flu virus has become antigenically different (or "antigenically drifted"), this generally means that the virus' antigenic properties are different enough that the body's immune system (i.e., a person's existing antibodies) will have a harder time recognizing and fighting against the virus.

When a flu virus has become antigenically different (or "antigenically drifted"), this generally means that the virus' antigenic properties are different enough that the body's immune system (i.e., a person's existing antibodies) will have a harder time recognizing and fighting against the virus.