Source: U.S. Centers for Disease Control and Prevention, Central Laboratory of Virology
Flu viruses constantly mutate, making it tough for our immune defenses to recognize the virus and combat it. Since the current strain of the H1N1 virus (known as swine flu) is relatively new, it may be more contagious than seasonal flu, although it seems no more virulent and most cases should be resolved without significant medical intervention. Here is a look at how flu infections spread: