Gerald is admitted to the hospital because he has pneumonia. His blood work shows a low number of T-cells. The doctor wants to order a test to see if Gerald is HIV positive. Why would the doctor do this? HIV attacks T-cells. If Gerald has HIV, he will have a lower T-cell count, and his immune system will be less able to protect him from other diseases. HIV attacks the pneumonia virus and uses cells to reproduce. If Gerald has HIV, he will also have pneumonia. Gerald may have taken antibiotics for HIV. These antibiotics would make his immune system more susceptible to pneumonia. Bacteria create an infection that strengthens the immune system to fight off HIV, but not pneumonia. This is why Gerald still has pneumonia.