The main source of TB infection is patient with Lung TB (different forms), especially with cavities. Infection shared with droplets by speaking, singing, coughing of sick person. During 2 years people with lo immunity became sick, another can be sick during their life. It depend from special factors, which enhancing or weakening the reaction of people to infection.

With regard to exposure to other types of infections (virus/bacteria/parasite/fungus) the sources depending of type of them - another people (hospital), environment (water, food, furniture, medical instruments, air). A devolopment of co-infection is actual in modern. It names nosocomial infection. This question related with program of epidemiological monitoring of nosocomial infection.

In addition to the answer given previously, tuberculosis was proven to spread through the air in close contact. It is transferred through coughing, sneezing, talking, laughing, etc in the form of airborne particles called droplet nuclei. This bacteria is released into the air and stays suspended until it is breathed in by another person. Mycobacterium tuberculosis is easily transmittable but not easy to acquire unless there is constant contact. Also, there are other factors such as smoking, particularly tobacco, that can increase the risk of tuberculosis in an individual.