A “bacillus carrier” is a carrier of infection. Even in the old days, this was the name given to those who were unable to recover and became carriers of a dangerous disease. After all, ancient medicine was inextricably linked with bacteriology. The transmission of infections could not yet be controlled, so the infection could easily be transferred from place to place. And if a person was infected with some kind of infection. The disease immediately became an obvious event, because an infectious person immediately fell under suspicion. And even the death of the bacilli carrier could lead to the spread of the disease throughout the environment. Also, such behavior could lead to the fact that the spread of viruses was facilitated by poor sanitary and epidemiological conditions in cities. This created unfavorable living conditions for the townspeople, and also led to the rapid development of many diseases. Treatment of such diseases was difficult. Therefore, vaccination has become perhaps the most ancient measure of disease control. Nowadays the meaning of the word has changed. Bacteria are called bacilli. Usually these are microorganisms of foreign origin for the body, that is, infections. The bacteria got their name from the microscope, one of the first researchers of which was the scientist Robert Hooke, known for his knowledge of human anatomy.