HIV is contagious from the time of infection until death. The HIV virus appears in the blood of a person with AIDS about 5-7 days after infection with the virus. In about 2 weeks, the virus replication in the body starts to be active and the level of virus in the blood increases dramatically, and the contagiousness increases. Also the latent phase of AIDS is somewhat contagious, but less so than the acute phase. AIDS destroys the immune system and causes serious damage to the immune system, leading to infection of all organs of the body and various types of complications, which can cause serious damage to the health of the patient and eventually even lead to death. In daily life, we should do our best to prevent AIDS, such as avoiding unclean sex or having multiple partners at the same time, avoiding unnecessary and irregular blood transfusions and injections, not sharing dental tools and razors with AIDS patients, staying away from drugs, and getting screened for AIDS before marriage. However, there is no need to be overly afraid of people with AIDS, as normal contact and communication will not lead to transmission.