The human immunodeficiency virus, or AIDS (acquired immunodeficiency syndrome) virus, is a virus that causes defects in the human immune system and was first discovered in the United States in 1981. It is a lentivirus, a type of retrovirus, that infects cells of the human immune system.
HIV is transmitted by HIV-infected individuals, who have been isolated from blood, semen, vaginal fluid, breast milk, etc. HIV is not transmitted by shaking hands, hugging, kissing, swimming, mosquito bites, sharing utensils, coughing or sneezing, or daily contact. The following are the three main modes of transmission: Sexual contact transmission HIV exists in the semen and vaginal secretions of the infected person, and sexual intercourse can easily cause a small break in the mucous membrane of the skin, through which the virus can enter the bloodstream and become infected. Sexual contact between people of the same or opposite sex can lead to HIV transmission. There is a large amount of virus in the semen or vaginal secretions of an HIV-infected person. During sexual activity (including vaginal sex, anal sex and oral sex), friction at the site of sexual intercourse can easily cause a small break in the genital mucosa, and the virus can then enter the bloodstream of an uninfected person. It is worth mentioning that the risk of anal intercourse is greater than that of vaginal intercourse because the intestinal wall of the rectum is more easily broken than the vaginal wall.
Blood transmission The risk of HIV infection is associated with the introduction of HIV-containing blood or blood products into the body, intravenous drug use, and transplantation of tissue and organs from an infected person or patient.
Mother-to-child transmission An HIV-infected woman can also pass the virus to her fetus during pregnancy and delivery. An infected mother can also pass the virus to her breast-fed child through breastfeeding.