infection by the human immunodeficiency virus
"HIV is an infection caused by the human immunodeficiency virus that weakens the immune system over time."
the virus that causes acquired immune deficiency syndrome (AIDS); it replicates in and kills the helper T cells
"The patient's declining health was traced to HIV, a virus that specifically targets and destroys his helper T cells."
Initialism of human immunodeficiency virus.
"The doctor explained that HIV stands for human immunodeficiency virus, a condition that weakens the immune system over time."
In plain English: HIV is a virus that attacks your immune system and makes it harder for your body to fight off infections.
"The doctor tested him for hiv to make sure his immune system was healthy."