Decreased immunity is a manifestation of AIDS, but decreased immunity does not necessarily mean that one is suffering from AIDS, it may also be caused by age, overwork, insufficient exercise, unhealthy heart, unbalanced diet, systemic diseases and other factors. AIDS is an infectious disease caused by human immunodeficiency virus (HIV) infection, which is mainly transmitted through sexual transmission, mother-to-child transmission and blood transmission. When HIV infects the human body, it will violate the body’s immune system, resulting in decreased or even absent immune function, and the body is susceptible to opportunistic infections or tumors, and ultimately often dies due to severe infections or malignant tumors. Although AIDS often results in a decline in immunity, a decline in immunity does not necessarily mean that one is suffering from AIDS. Usually with age, the body’s immunity will also decline, long-term overwork, unbalanced diet, insufficient exercise, degenerative changes in the thymus or lymph nodes, etc., will affect the normal physiological functions, which will lead to a decline in immunity. There are also a variety of systemic diseases such as tumors that can lead to decreased immunity. Patients are advised to look at the causes of immunity decline scientifically. If you suspect that you have AIDS, you need to go to the dermatology and venereal diseases department of regular hospitals, infectious diseases department and other departments in a timely manner, and make a clear diagnosis under the guidance of a professional doctor.