Tuberculosis (TB) is the odd one out because it is caused by bacteria (Mycobacterium tuberculosis), while the other three - AIDS, Chickenpox, and SARS - are all viral diseases. AIDS is caused by HIV, Chickenpox by Varicella-zoster virus, and SARS by SARS-CoV virus. Additionally, TB spreads through airborne droplets rather than direct contact or bodily fluids like the others.