Acquired immunodeficiency syndrome, more commonly known as the AIDS epidemic, is a set of symptoms following the destruction of immune system cells by the human immunodeficiency virus (HIV). AIDS is the last stage of HIV infection when immunosuppression is severe. It leads to death from opportunistic illnesses. A person with AIDS is referred to as "AIDS" or more 
Three modes of transmission were observed:
By sexual means, which is the main means of contagion;
Blood transfusion: particularly for injecting drug users and health professionals (until the late 1980s, transfused patients, particularly hemophiliacs, were also at risk, seeing contaminated blood);
From mother to child: which can occur in utero in the last weeks of pregnancy, at the time of delivery and breastfeeding.
A pandemic developed from the late 1970s, making the disease a global health problem. Prevention, such as condom use, is by far the best option because there is currently no vaccine available to protect against the virus, and current antiviral therapies do not provide cure. While effective, they can only stop the proliferation of HIV within the body and not eradicate it. Moreover, these costly therapeutics are readily available only in developed countries that can afford the financial burden; In developing countries, more than 95% of patients now receive no effective treatment. For this reason, the UN, through its UNAIDS program, has made the fight against AIDS one of its priorities.