in epidemiology, the place where the source of the causative agent of an infection (a sick person or bacteria carrier) resides and the area adjacent to that place; that is, the area that poses a threat of transmitting infection to surrounding individuals.
The boundaries of an epidemic focus are determined by the characteristics of the infection and by the specific conditions that encourage the disease to spread. In typhus, for example, the epidemic focus may be an apartment house, hostel, barrack, or populated point—that is, the residence of the human host, where other individuals may come into contact with him and where infected lice may infest various objects. In measles, the epidemic focus may be an apartment house or a children’s institution—that is, the residence of the sick child and of other persons who may have come into contact with him. An epidemic focus may be multiple, with several cases of the disease found within a group (classroom, industrial plant, home).
An epidemic focus is considered liquidated when the source of the causative agent is isolated and treated (for example, after hospitalization), when it is certain that the disease is absent (taking into account the maximum length of the incubation period) and that there are no bacteria carriers among the individuals who came into contact with the human host, and when disinfection (disinsectization, deratization) has been carried out.