AIDS is caused by the human immunodeficiency virus (HIV). Today, the disease is mainly transmitted through unprotected sex and infected hypodermic needles. The immune system is weakened to such an extent that the body can no longer fight infections. Vaccinations once morest AIDS are not yet available. However, the replication of the HIV virus can be stopped with antiretroviral therapy (ART). If this is used at an early stage, infecting other people can also be avoided. In addition, the life expectancy increases in the normal range.