AIDS is a disease caused by HIV infection of the immune system, which leads to a decline in CD4 cells and a decrease in immune function, resulting in opportunistic infections and tumors. The most common opportunistic infection is Pneumocystis carinii pneumonia, which is characterized by recurrent low-grade fever, cough, and chest tightness, and the symptoms of chest tightness may worsen progressively and even cause respiratory failure. Patients need to be hospitalized in time, otherwise the disease will progress further and may become life-threatening due to respiratory failure.