What is a potential consequence of untreated HIV infection?

In the context of untreated HIV infection, the development of opportunistic infections is a significant concern. HIV primarily targets the immune system, specifically the CD4 T cells, which play a crucial role in fighting off infections. As the infection progresses and CD4 cell counts decline, the body's ability to respond effectively to pathogens diminishes. This deterioration of the immune system opens the door for opportunistic infections – infections that take advantage of the weakened immune system. These can include illnesses caused by viruses, bacteria, fungi, and parasites that would not typically cause disease in individuals with healthy immune responses.

In contrast to the correct choice, the other options suggest outcomes that would not occur with untreated HIV. Increased muscle mass, improved immune response, and increased energy levels represent positive health conditions that are not consistent with the effects of the virus on the immune system. Instead, untreated HIV typically leads to the opposite scenario, with muscle wasting, decreased immune function, and fatigue becoming more prevalent as the condition advances.