How does the human immunodeficiency virus (HIV) affect the body?

The human immunodeficiency virus (HIV) primarily affects the body by weakening the immune system. This virus specifically targets CD4 cells, which are crucial components of the immune system. As the virus replicates and spreads, it reduces the number of these cells, making the body more vulnerable to infections and diseases. This immune deficiency is the hallmark of HIV infection, leading to acquired immunodeficiency syndrome (AIDS) if not treated effectively.

While fever and fatigue can be symptoms associated with HIV, they are not the primary or defining impact of the virus. High blood pressure and stomach pain are not directly related to the action of HIV on the immune system. The most significant and direct effect of HIV is its capacity to compromise immune function, which is why this answer is the most accurate in the context of understanding how HIV impacts health.