AIDS is the name of a disease. Both humans and some species of monkeys can get it. It is caused by a virus. This virus weakens the immune system: this is the "police" in the body that normally fights invading pathogens. That's why AIDS makes you sick with all kinds of other diseases. The name of the virus, however, is not AIDS virus, but HI virus, or HIV for short.
HIV is the abbreviation for "Human Immunodeficiency Virus". It is also called "human immunodeficiency virus". The virus passes from one person to another in the blood. This usually happens when two people give each other drugs with the same syringe or when a doctor does not work cleanly. People who get the virus do not necessarily feel anything. However, one can get tested in a hospital. Anyone who carries the virus is HIV positive.
In order to survive, HI viruses must penetrate cells. Cells in the blood are particularly suitable. But not only there: They like to live in the mucus inside the female reproductive organs, as well as under the foreskin of the penis. They also feel at home in the seminal fluid of men.
When the viruses have multiplied enough, they can weaken the immune system. This can happen quickly or take many years. When the disease has broken out, the person has AIDS. Then various diseases can break out: Fever, fatigue, headache, poor appetite, joint pain, muscle pain, nausea, and diarrhea. Later, the affected people may get cancer or become sick from bacteria that are normally harmless.
Some people stay healthy for ten years or more, but some die quite quickly from it. Today there are also drugs that help very well. They can often prolong the time until the disease fully breaks out. But they cannot cure a patient completely. In most cases, however, the patient can no longer infect other people.
The word AIDS is an English abbreviation. Translated, the full term means "acquired immunodeficiency syndrome." Immune deficiency or immunodeficiency means that the body is not immune enough, that is, it cannot protect itself well enough against infection. "Syndrome" is said when several signs of a disease occur together.