In the opinion of the US Institute of Medicine, the next major infectious disease threat to the United States may be, like HIV, a previously unrecognized pathogen. Barring that, the most likely known infectious diseases to directly and significantly impact the United States over the next decade will be HIV/AIDS, hepatitis C, and multidrug resistant TB, or a new, more lethal variant of influenza. Foodborne illnesses and hospital-acquired infections also pose a threat.

CDC Raises Alarm Over New Form Of Pneumonia
by Dr. Gary Farr 3/16/2003
The U.S. Centers for Disease Control and Prevention recommended Saturday that Americans consider delaying nonessential travel to countries affected by an outbreak of a rapidly spreading, severe form of pneumonia that does not appear to respond to treatment.