HIV-infection - chronic infectious disease: (HIV) causes a human immunodeficiency virus and is characterized by the lesion of the immune system leading development of a syndrome of got immune deficiency (AIDS) and morses of the patient as a result of development of secondary (opportunistic) infections, malignant tumours or lesions of the central nervous system (a subacute encephalitis).

Transfer of a virus at a hemotransfusion, use of the medical instruments polluted by a blood of patients, at transplantation of tissues and organs, during pregnancy and sorts - from mother is proved to a fetus, at thoracal feeding - from mother to the child and in rare cases - from the child to mother. According to the world organization of public health services, sexual it is by infected with a HIV of 75 % parenteral by - 15 % of patients. However these parities are unstable: so, use of condoms leads to depression of frequency of infection at sexual contacts, the control over donors reduces risk of infection at a hemotransfusion, the partus caesarius reduces probability of infection of the child.