HIV symptoms typically begin to show up about 2 to 4 weeks after exposure to the virus. This early stage, called acute retroviral syndrome or acute HIV infection, often presents flu-like symptoms such as fever, chills, headache, tiredness, swollen lymph glands, rash, sore joints or throat, and weight loss. However, some people do not experience noticeable symptoms at this stage. More serious or longer-lasting symptoms may take years to appear. Testing is the only definitive way to know if someone has HIV, especially since people can be infectious even without symptoms during early stages.