Primary infection
This first phase may be accompanied by flu-like symptoms such as fever, sore throat, muscle pain, fatigue, swollen lymph nodes, and rash.
These symptoms, which disappear after a few weeks, do not appear in everyone who is infected. The primary infection sometimes goes unnoticed. It is during this stage that the immune system produces antibodies to defend itself against the virus.
Source: The Essentials of HIV / AIDS, Portail VIH / SIDA du Québec, Benoît Lemire