HIV, the virus that can develop into AIDS, attacks the immune system. It typically takes many years after infection with the HIV virus for the virus to multiply sufficiently to cause AIDS; most infected people experience few symptoms in the years after infection. Shortly after infection, however, many people develop a short-lived, mild illness called "acute HIV infection," the result of the body's initial response to invasion by the virus. Acute HIV infection is easily confused with other viruses such as the flu or colds, but it does have a set of typical and recognizable symptoms.
Headache and Fever
According to MayoClinic.com, signs of acute HIV infection first show up about two to four weeks after initial infection. One sign of early infection is a headache, often accompanied by fever. Unfortunately, headache and fever are common to many viral infections, meaning it can be difficult to discern whether the headache and fever are due to HIV. Still, people who have recently engaged in HIV risk-associated behaviors, such as having unprotected intercourse or sharing IV drug needles, should see a physician about any unexplained headaches or fevers in the weeks following exposure.
Fatigue
AIDS.org warns that another common symptom of acute HIV infection is unexplained fatigue. This is because the body's immune system works very hard to fight any invading pathogens, and the HIV virus is no exception. When the virus first enters the body, it's detected by the cells of the immune system within hours. The virus begins to multiply, outstripping the ability of the immune system to fight it off. The more the virus proliferates, the harder the immune system works, leading to symptoms of fatigue within a few weeks of infection. AIDS.org says HIV tests during acute HIV infection typically come back negative, because testing is for antibodies to the HIV virus, which have not yet been produced. Instead, it's recommend you take viral load tests, which count the number of viruses in a sample of blood.
Other Signs of Immune Activation
Other common, non-specific signs of immune system activation often show up in the early weeks of HIV infection. Like many other symptoms of early HIV, these are difficult to diagnose, because they're common to many illnesses. Still, the University of California at San Francisco notes that rashes are not uncommon in acute HIV infection. Also, the lymph nodes swell with early HIV, as they do with many infections. Lymph nodes are clusters of immune tissue that plump up with blood and cells during acute infection. It's possible to feel them in the upper neck, armpits and groin. Swollen lymph nodes are quite enlarged and may feel sore.
