The window period of HIV is the period of time when you are infected with HIV but your body has not yet developed antibodies. Although the antibody is negative during this period, it is also infectious because the virus is already present in the body. When the human body is infected with HIV, it invades the immune system, destroys immune cells and causes a decline in CD4 cells, which leads to various opportunistic infections and tumors. The main cause of death in AIDS patients is opportunistic infections, the most common ones being Pneumocystis carinii pneumonia. Therefore, once AIDS is diagnosed and antiretroviral treatment is indicated, one needs to go to the local CDC for antiretroviral treatment in a timely manner.