Which virus can cause retinitis in individuals with a weakened immune system?

Cytomegalovirus (CMV) is a member of the herpesvirus family and is well-known for its potential to cause retinitis, particularly in individuals with compromised immune systems, such as those with HIV/AIDS or undergoing immunosuppressive therapies. In the context of AIDS, for example, CMV can reactivate and lead to significant ocular complications, including retinitis, which can result in vision loss if not treated promptly.

The reason CMV is particularly relevant in this situation is its ability to remain latent within the body and reactivate when the immune response is weakened. This capacity to cause disease primarily in immunocompromised individuals sets it apart from other viruses such as HIV or hepatitis B, which, while they affect the immune system, do not directly lead to retinitis. Influenza is primarily a respiratory virus and does not typically cause retinitis, even in immunocompromised patients. Therefore, the connection between Cytomegalovirus and retinitis in those with weakened immune systems underscores its significance as the correct answer to this question.