There are quite a few factors that affect the contagion of tuberculosis. 1, the more coughs and sputum a TB patient coughs, the more chances of bacterium excretion, the greater the infectiousness. 2, TB patients with positive sputum test are more contagious. 3.The degree of ventilation in the living room is small, and it is easy to be infectious. 4, contact with TB patients for a long time, close, easy to be infectious. 5.Susceptible people are easy to be infected. 6. Generally, the infectiousness is greatly reduced after 2 weeks of chemotherapy, which is called “chemical isolation”, and treating patients is the best measure to eliminate the source of infection and infectiousness.