Which disease is caused by human immunodeficiency virus (HIV)?

Human immunodeficiency virus (HIV) is the causative agent of acquired immunodeficiency syndrome (AIDS). HIV attacks and gradually destroys the immune system, specifically targeting CD4+ T cells, which play a crucial role in the body's ability to fight off infections and diseases. As the infection progresses without treatment, the immune system becomes increasingly compromised, leading to the development of AIDS. This stage is characterized by a significant increase in the susceptibility to opportunistic infections and certain cancers that are associated with a weakened immune response.

In contrast, the other diseases listed—such as influenza, hepatitis, and syphilis—are caused by different pathogens and mechanisms. Influenza is caused by the influenza virus, hepatitis can be caused by various viruses including hepatitis A, B, or C, and syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. These conditions do not arise from HIV infection, highlighting the specificity of HIV for leading to AIDS.