TB, also known as tuberculosis, is transmitted via the air, so speaking, spitting, coughing and sneezing by an infected person can send TB bacterium into the air where it is inhaled by healthy individuals and spreading the infection, as noted by the United States Centers for Disease Control and Prevention. TB can be both latent or active, and it usually attacks the lungs of the infected individual. Latent TB can be carried around for life without the infected person ever experiencing any symptoms or transmitting it to others.
TB spreads from one person to another, but it doesn't always cause an active TB infection. Latent TB occurs whenever TB bacteria live inside a person, but the person's immune system attacks the bacteria and stops it from multiplying. Those people with latent TB do not feel ill and are asymptomatic. Nonetheless, the CDC warns that if the bacteria becomes active and begins to multiply, the person may fall ill.
When the immune system is not successful in halting the growth of the TB bacteria, it multiples and causes an active infection that is transmittable to others. Symptoms of TB disease include a bad cough lasting for 3 weeks or more, chest pain, coughing up sputum or blood, weight loss, no appetite, chills, fever, weight loss and night sweats.