The most serious manifestation of AIDS is in the late stages of the disease, when the immune system is weakened, causing various opportunistic infections that may eventually lead to death. The main cause of AIDS is the damage of lymphocytes and the imbalance of immune cell ratio caused by HIV infection, which leads to the disruption of the immune system, thus triggering opportunistic infections in various parts of the body. When the lungs are infected, pneumosporidiosis and severe pneumonia will occur; when the nervous system is infected, dementia and toxoplasmosis encephalopathy will easily occur; when the blood system is infected, lymphoma and sepsis will occur, which may ultimately lead to the death of the patient. Therefore, the harm of AIDS is mainly the attack on the immune system, and the most serious manifestation is the lowering of the immune system, which leads to infections of the lungs, the nervous system, and the blood system, resulting in serious complications. It is recommended that you must pay attention to protect yourself, do not share personal belongings, reduce the number of unclean sexual intercourse, and so on.