Concept:Viruses cause specific diseases such as measles, smallpox, and poliomyelitis, while other diseases may be caused by bacteria or different pathogens.Explanation:Measles, smallpox, and poliomyelitis are all caused by viruses.Tuberculosis is caused by the bacterium Mycobacterium tuberculosis, not a virus.Therefore, tuberculosis is the only listed disease whose pathogen is not a virus.Answer:A. Tuberculosis