API stands for Application Programming Interface, i.e. API is the way for an application to interact with certain system/application/library/etc. For example, there are API's for OS (WinAPI), API's for other applications (like databases) and for specific libraries (for example, image processing), etc.
Acute HIV infection: The first stage of HIV, known as the primary or acute infection, may cause symptoms of fever and skin rash. This is because the virus is multiplying rapidly in the body and infecting immune cells. This phase generally lasts several weeks.
A fever occurs when the body increases in temperature. Most common cause of this is an infection of some kind. The White blood cells that eat the infection, release chemicals that go to the brain and tell it to raise the temperature of the body. The brain has a set point for our temperature, 98.6F.