Primary HIV infection is the first stage of HIV disease, when the virus first establishes itself in the body. Some researchers use the term acute HIV infection to describe the period of time between when a person is first infected with HIV and when antibodies against the virus are produced by the body (usually 6- 12 weeks).
Some people newly infected with HIV experience some "flu-like" symptoms. These symptoms, which usually last no more than a few days, might include fevers, chills, night sweats and rashes (not cold-like symptoms). Other people either do not experience "acute infection," or have symptoms so mild that they may not notice them.
Given the general character of the symptoms of acute infection, they can easily have causes other than HIV, such as a flu infection. For example, if one had some risk for HIV a few days ago and are now experiencing flu-like symptoms, it might be possible that HIV is responsible for the symptoms, but it is also possible that he/she has some other viral infection.