Final answer:
The disease caused by a virus that infects T cells is acquired immune deficiency syndrome (AIDS).
Step-by-step explanation:
The disease caused by a virus that infects T cells is acquired immune deficiency syndrome (AIDS). AIDS is not a single disease but a set of diseases that occur when helper T cells fall to a very low level, making it difficult for the affected person to fight various diseases and infections. These diseases are usually the cause of death in people with AIDS.