Since pulmonary tuberculosis is a contagious disease, you can transmit Mycobacterium tuberculosis to people around you. However, it is known that the contagiousness decreases sharply when tuberculosis medicine is taken, and disappears after taking medicine for about two weeks.

However, the period of contagiousness varies depending on the patient's symptoms, severity of the disease, and degree of resistance to Mycobacterium tuberculosis. The time to return to the workplace or school should be determined through consultation with a physician.

During the initial contagious period of tuberculosis treatment, you can wear a mask and stay at home, but you should refrain from going out to public places. If you have a newborn or an immunosuppressed patient at home, or if you have difficulty finding a separate, well-ventilated space, you are recommended to stay at the hospital for treatment during the contagious period.

Tuberculosis spreads when Mycobacterium tuberculosis, released into the air when a person with tuberculosis coughs, enters the lungs of other people when they breathe it in. However, even when Mycobacterium tuberculosis has entered the lungs, tuberculosis infection does not occur if it is eliminated by innate immunity.

Latent tuberculosis infection: The condition where Mycobacterium tuberculosis overcomes innate immunity and proliferates is called infection. In this case, the immune response works to suppress Mycobacterium tuberculosis. This condition can be identified with a skin or blood test before symptoms appear and is called latent tuberculosis infection. About 30 percent of contacts with contagious tuberculosis patients will develop latent tuberculosis.

Latent tuberculosis is a condition where the patient is asymptomatic, has not developed the disease, and is not contagious. In South Korea, the prevalence of tuberculosis is high, and the positive rate is so high to the extent that 20-30% of the population show a positive reaction to tuberculin due to the effect of BCG vaccination.

About 30% of contacts of contagious tuberculosis patients develop latent tuberculosis, and 10% develop tuberculosis within 2 years. Therefore, latent infection should be carefully managed for early diagnosis and treatment of tuberculosis.  

Tuberculosis onset: Usually, 10 to 20% of people infected with tuberculosis develop the disease over their lifetime. About half of them develop tuberculosis within 2 years after infection, and the remaining half develop it later. About 80 to 90% of people infected with tuberculosis do not develop the disease for the rest of their lives, but in the case of people with a latent infection, preventive treatment or regular chest X-ray examinations are required to monitor the development of tuberculosis.

Tuberculosis (TB) is an infectious disease caused by the bacterium Mycobacterium tuberculosis.

When a person with tuberculosis coughs, Mycobacterium tuberculosis is released into the air, and when people around the person breathe in the air, it enters the lungs and infects them. Tuberculosis mostly occurs in the lungs, but in about 15% of cases it can also develop in other organs such as lymph nodes, bones, and intestines.

Unlike other bacteria, Mycobacterium tuberculosis proliferates very slowly, so it has a long incubation period, which is asymptomatic after infection. Since tuberculosis has no specific symptoms unique to it, it is difficult to diagnose with symptoms alone, and the treatment period after diagnosis is long. Therefore, continuous management of patients and contacts is very important.

Because latent tuberculosis is not transmissible, those diagnosed with it should not be misunderstood to be tuberculosis patients. People with latent tuberculosis are those who have recently been exposed to Mycobacterium tuberculosis, but Mycobacterium tuberculosis cannot be found because it is insignificant and naturally there is no possibility of infecting others. However, people diagnosed with latent tuberculosis are very important in terms of tuberculosis management because based on the results of follow up it is known that 5% of them develop true tuberculosis such as pulmonary tuberculosis within 1 year and 10% during their lifetime, and new infections from them can occur again. Therefore, along with treating diagnosed tuberculosis patients, preventing the possibility of tuberculosis by administering an appropriate drug to latent tuberculosis patients is very important. These people are just considered to have latent tuberculosis and managed and it does not mean that they are actually contagious. People with latent tuberculosis should usually visit a public health center to get the necessary tests and medications, but for the convenience of KAIST members, they are currently provided with these through the KAIST Clinic with the budget of the school.

 The tuberculin (PPD) test is a representative test to determine whether a cell-mediated immune mechanism has occurred due to tuberculosis infection.

 The test is performed by injecting tuberculin solution into the examinee's forearm with a small needle on the first day of the visit, and then the examinee visits again 48 to 72 hours later to measure the degree of skin reaction at the injection site. If the result is read when 72 hours have passed, the accuracy will decrease. Therefore, the result should be read with the set time.

Once established, a cell-mediated immune response has a lifelong lasting effect, so tuberculin-positive reactions occur not only in people who are currently infected but also in those who have previously been infected and were completely treated.