How is tuberculosis transmitted?

Tuberculosis is a chronic infectious disease that usually affects the respiratory system, although it may involve the lymph nodes, urogenital area, skin, eyes, joints and bones. In recent years, the number of infected persons has been steadily increasing. Given the real possibility of infection, it is necessary to clearly understand how pulmonary tuberculosis is transmitted.

Ways of transmission

The causative agent of tuberculosis is transmitted from a person suffering from an open form of the disease in which mycobacteria are released into the environment.

Is closed tuberculosis transmitted? This is possible with prolonged and close contact with a carrier of mycobacteria - when living together, working, in places of detention, etc.

The leading route of transmission of the disease is airborne. Other methods - alimentary (food) and contact - are of much less importance. Intrauterine infection is very rare.

Airborne droplets

The spread of infection occurs when a patient with tuberculosis coughs, sneezes, or talks with particles of his sputum. Microscopic droplets of secretions from the respiratory tract can spread for several meters around (the greatest danger is being in an area up to 1 meter in front of the patient).

The dust-air path of the transmission of the pathogen is a variant of the previous one. In this case, sputum and saliva settle on objects, dry out and turn into infected dust. Due to its high resistance, mycobacteria are viable in the environment for a long time (several weeks).

Inhalation of contaminated aerosol or dust does not always lead to disease development. During normal functioning of the immune system, mycobacteria are “immured” in a microscopic pulmonary focus, which can exist for many years without any manifestations (latent form of the disease). In the case of a weakening of the body by starvation, trauma, infection, diabetes mellitus, the activation of the process with the transition to the expanded stage is possible.

The aerogenic route of spread of tuberculosis is of decisive epidemiological significance. This can be judged by how the open form of tuberculosis is transmitted, in which a patient in a year can cause more than ten people to become infected.

Alimentary route

Food contamination occurs when eating foods contaminated with infected sputum, as well as when using milk (butter, cream and cheese based on it), obtained from sick cows (they may have a bovine type of mycobacterium that is dangerous to humans).

The infectious dose in the alimentary route of transmission is much higher than in the aerogenic one. This is due to the bactericidal effect of gastric juice (especially in persons with high acidity).

There are cases of self-infection in which the patient swallows his own contaminated sputum. This process can cause the spread of tuberculosis throughout the body and the emergence of extrapulmonary forms (damage to the mesenteric lymph nodes and other organs).

Contact route

Since the skin of a healthy person is sufficiently resistant to the effects of the pathogen, contact transmission is quite rare. In this case, cases of occupational infection are important - during the milking of sick cows, mycobacteria can penetrate through the damaged skin of the hands. The episodes of infection of pathologists and forensic experts during the autopsy of corpses of persons suffering from tuberculosis are described.

The likelihood of illness increases with a decrease in immune function and in childhood. There is acute tuberculous conjunctivitis, obtained by contact.

In utero infection

Is tuberculosis inherited? No, as it is not a genetic disorder. In very rare cases, infection of the fetus from a sick mother is possible - this usually occurs with a neglected process and social disadvantage. Variants of pathogen transmission:

  • intrauterinely with placental lesions,
  • during childbirth during the passage of the birth canal,
  • directly in the postpartum period.

The rarity of this situation is due to the high protective properties of the placenta, due to which even women with open tuberculosis usually have healthy children. Provided postpartum isolation from the mother and vaccination of the child, the child almost never develops the disease.

To prevent infection with tuberculosis, it is necessary to observe hygiene rules, regularly perform fluorography and consult a doctor in the presence of alarming symptoms.

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