Abstract: The full medical name of AIDS is "Acquired Immunodeficiency Syndrome", or "AIDS" for short. It is an immunodeficiency syndrome caused by human infection with HIV.

Most people infected with HIV are still healthy and can live for many years without symptoms or only minor diseases. Even if they look healthy and feel healthy, they can still transmit HIV to others, which is lifelong infection.

HIV has strict host specificity, which can infect humans and lead to AIDS. Under the experimental conditions, HIV- 1 can infect chimpanzees, and HIV-2 can infect rhesus monkeys, which can cause disease and seropositivity, but it will not cause animal diseases. The virus can be isolated from peripheral blood, semen, milk, cerebrospinal fluid, saliva, tears and other body fluids of HIV-infected people, but there are no body fluids such as tears and saliva at present.

(1) Sexual transmission, which is spread between gay men and heterosexuals through sexual behavior, or through artificial insemination;

(2) Blood transmission refers to accepting blood or organs donated by HIV-infected people, using blood products contaminated by HIV or using injection needles with HIV-infected people and being infected. In addition, medical staff and laboratory workers who come into contact with body fluids or HIV cultures of HIV-infected people are exposed to occupational risks of HIV infection;

(3) Mother-to-child transmission. Mothers with HIV can transmit HIV to their newborns in utero or during childbirth (Connor, 1997). Moreover, ordinary contact between people will not lead to the spread of HIV, so there is no need to be overly sensitive and afraid of it.

In vitro, HIV can infect CD4+T lymphocytes (T4 cells) and monocytes-macrophages, which proliferate and cause cytopathic effects, indicating that CD4+T lymphocytes and monocytes-macrophages are the main target cells of HIV. In addition, HIV can also infect normal B lymphocytes, B lymphoblastoid cell lines, microglia, glial cells, neutrophils and various cell lines transformed by EB virus (O').

In vivo, HIV not only infects CD4+T lymphocytes, monocytes-macrophages, B lymphocytes, neutrophils and follicular dendritic cells in connective tissues, but also infects Langerhans cells in epithelial tissues and microglia, oligodendrocytes, astrocytes and brain endothelial cells in nerve tissues, which are distributed in bones, thymus, brain, heart, lung and intestine. Skin, gonads and other organs (Dittmar, 1997a). HIV has such a wide range of cell and tissue tropism, which is consistent with the symptoms of CD4+T lymphocyte deficiency, lymphadenopathy, Kaposi's sarcoma and the nervous system damage caused by it.

High variability is a remarkable feature of HIV and other retroviruses. Mutations mainly come from the reverse transcription process, among which env, nef and other genes have the largest variation range, while gag and pol are relatively conservative and have low variation degree, mostly silent point mutations. According to the variation of env and gag genes, HIV- 1 can be divided into at least two groups. *** 1 1 subtype. Among them, M (main group) is composed of 10 subtype, that is, subtype A-J. In Europe and America, subtype B is dominant, while subtypes A, C, D and E are prevalent in Africa. In China, subtype B is dominant, followed by subtype C and subtype A; In addition, there are mosaic phenomena among subtypes of M group, such as A/E, G/A, etc. O (outlier) group is mainly distributed in Bai Xi and Central Africa, and is often regarded as a subtype (O subtype) because of its few members. According to the same method, HIV-2 can be divided into subtype A and subtype B (UNAIDS, 65438). Even within the same body, the difference is obvious. In fact, every HIV infected person carries a heterogeneous virus group, and there are various variants in the body. High variability helps HIV escape the immune surveillance of the host, and also sets a huge obstacle for the prevention, diagnosis and treatment of HIV infection.

How to prevent AIDS According to different transmission routes, scientists suggest that the following measures should be taken:

1, prevention of sexual transmission of AIDS

Lead an honest and clean life and maintain a loyal and exclusive sexual relationship;

Use condoms correctly when having risky sex;

Timely treatment of sexually transmitted diseases.

2. Prevent the blood transmission of AIDS.

Do not use untested blood and blood products.

Don't take drugs, and don't use needles to take drugs with others.

Ear piercings, body piercings, tattoos, acupuncture therapy or any process that requires invasive skin puncture are all at risk of spreading HIV.

3. Prevention of mother-to-child transmission

HIV can be transmitted during pregnancy, childbirth or breastfeeding after the birth of a child.

Women infected with HIV should avoid pregnancy, such as induced abortion.

Using antiviral drugs before and after delivery can reduce the probability of mother-to-child transmission.

Artificial feeding can also reduce the risk of HIV infection.