Pathogen Bacillus tuberculosis is a slender, slightly curved and rod-shaped bacteria, in the medium is nearly spherical short rod or long chain, about 1-10um long, about 0.2-0.6um wide. Bacillus tuberculosis divides slowly, about 20-30 hours once, does not have flagella, and does not move, is an aerobic acid-resistant bacteria. There are no studies that indicate that it produces endotoxins or exotoxins, so there is no immediate reaction to infection. Its cell wall contains many lipids and proteins, and it is very resistant to the outside world, and can survive for 6-8 months in the shade. When an infectious tuberculosis patient spits or sneezes, the sputum containing tuberculosis bacilli has a chance to become tiny droplets floating in the air, with the tuberculosis bacilli in the center of the droplets and the sputum around them. defense mechanism of the host, and come into direct contact with alveolar macrophages. If the number of inhaled tuberculosis bacilli is small, the virulence is not strong, and the ability of host macrophages to kill tuberculosis bacilli is relatively sufficient, it will not lead to infection. However, if all conditions are unfavorable for the host, the TB bacilli may begin to proliferate. Infection After about 6-8 weeks of multiplication of the tuberculosis bacilli in the body, the antigens are sufficient to trigger a cellular immune response in the host, leading to caseous necrosis, the so-called delayed allergic reaction. After the host immune control process, the initial lesion usually improves naturally and does not develop immediately, but at this time the TB bacilli are not completely cleared and there are still a few TB bacilli lurking in the body waiting for an opportunity to develop. If the host’s cellular immune system is incompetent, the bacillus may use the initial lesion as the basis for the onset of disease, i.e., primary tuberculosis, which is usually childhood tuberculosis, tuberculous meningitis, and cornified tuberculosis. Onset After this infection, the tuberculin skin test is positive; after the initial infection, the lifetime chance of reactivation of the tuberculosis bacilli in the body and onset of disease is about 5-10%, of which about half develop in the first 5 years of infection, the risk is greatest in the first year, and decreases each year thereafter, but there is a lifetime chance of onset. In HIV-positive individuals, the annual risk of developing tuberculosis is as high as 7-10% (Selwyn, 1989), which also increases the risk of latent tuberculosis becoming active nearly 100-fold. In children younger than 5 years of age, the lifetime incidence of TB infection by a caregiver can be as high as 20-40%, much higher than in children older than 5 years of age, and can be hundreds to thousands of times different from the incidence in children of the same age. The time from infection to disease onset can be as short as a few weeks to about 2 years. Tuberculosis occurs in the lungs and in all organs of the body, such as the lymph nodes, bones, kidneys, brain, skin, and reproductive organs. Not everyone with tuberculosis is infectious. First, patients with simple extrapulmonary tuberculosis are not infectious, and second, when someone is claimed to have tuberculosis, they may have inactive tuberculosis and the lesions are already calcified and scarred, so of course they are not infectious. Even in patients with active TB, there are contagious (sputum test reveals TB bacteria) and non-contagious, and the latter is not contagious. When an infectious TB patient spits, coughs or sneezes, the sputum containing TB bacilli has a chance to become droplets and float into the air, with the larger droplets falling directly to the ground and the smaller ones evaporating immediately. According to a study, there is only one effectively infected droplet in about 11,000 cubic meters of air in a ward that houses TB patients (Riley, 1962), so it is not as much as one might think. How to protect yourself Treatment is the best protection Current TB drugs are very effective, and although it takes more than six months to treat a case until it is less likely to recur, as long as the medication is taken regularly and in a timely manner, the infectiousness of an otherwise infectious case can be reduced in a very short period of time. Therefore, it is the most important principle of our codefense staff to visit cases diligently, monitor their treatment closely, and ensure that every TB drug prescribed by the doctor is taken regularly. Sputum testing is the only way to know if a case is dangerous. Only infectious TB patients have more contagious friends and relatives around them, so the TB prevention staff should pay attention to the sputum testing of cases and actively follow up on those who have had sputum testing. Only when the sputum test results of all patients in hand are fully grasped can we talk about how to protect ourselves. Do not neglect the importance of sputum testing because of the lack of timeliness as it takes 2 months for sputum culture of TB bacteria. According to a study by the World Health Organization, patients with positive sputum smears are the most infectious, and the risk to their friends and family is statistically significant. By making good use of sputum smear tests, we can still define the infectiousness of a case early and protect ourselves. Pay attention to room ventilation As mentioned above, TB patients do not produce many effective infectious particles, so if we can educate patients and their families to pay attention to room ventilation, we can also reduce the chance of being infected. If you visit a TB patient, the first thing you do when you enter the house is to open every window, and then you start asking questions and instructing the patient. Interviewing skills When interviewing TB patients, sit on the side of the patient and avoid facing each other as much as possible. Personal protective tools Most young healthy caregivers in areas with low to moderate TB prevalence have not been infected with TB. Therefore, it is recommended that health caregivers should make good use of personal protective equipment to protect themselves from infection until they come into contact with patients who are sputum smear-positive, or who are not yet receiving effective drug therapy, or who are already on treatment but are not easily reversible (e.g., severe cavitary, multi-drug resistant TB). For example, surgical masks (paper masks or wet masks are not effective) and protective measures for family members who have been exposed for long periods of time, but have young children or immunocompromised family members living with them, can reduce their exposure to infection.