Carriage of infectious agents
The preservation of pathogens of infectious diseases in the body of a practically healthy person and their release into the external environment is called carriage of infectious agents (C.v.i.). N.v.i. may occur in convalescents (who have recovered from illness and are in the recovery stage).
Special cases of N.v.i. may be bacterial carriage - carriage of pathogenic bacteria, or virus carriage - carriage of pathogenic viruses. The duration of the release of pathogenic microbes may vary. Under favorable conditions it usually ends within a few weeks. This form of carriage is observed in the majority of recovered or healthy people who were in contact with the patient.
Carriage that continues for a long time, even years, is called chronic. Chronic N.v.i. It is usually observed only in those who have recovered from the disease. The duration of carriage in these cases is often supported by concomitant diseases.
When the body's defenses are weakened, N.v.i. may develop into a severe disease. Isolation of pathogens from carriers occurs in the same way as in cases of severe disease. It can be permanent or periodic.
N.v.i. is detected by laboratory methods and is of great epidemiological significance, because an undetected carrier may be a source of infection.
To prevent infectious diseases associated with N.V.I., the necessary measures were taken in the USSR: discharge of those who had been ill only after testing for carriage, treatment to free them from pathogens, registration and examination of those who had recovered, examination of people working in children's and medical institutions. When identifying N.v.i. such persons were excluded from work.