Early identification and immediate treatment of individuals newly infected with HIV is important for two reasons: it benefits the long-term health of the infected patient, and it reduces onward HIV transmission. Primary HIV infection (PHI) reflects the period following HIV acquisition during which viraemia bursts until the establishment of a stable plasma HIV-RNA level approximately six months post infection. During this period, patients are particularly contagious and are often unaware of the infection. As a consequence, PHI disproportionally affects onward transmission. During PHI the immune system is irreparably damaged and persistent viral reservoirs are formed. Initiating antiretroviral therapy (ART) during PHI could potentially lead to a functional cure through early and prolonged viral suppression. Unfortunately, symptoms of PHI are nonspecific and the diagnosis is frequently missed. This impedes timely diagnosis and prompt initiation of ART. To increase awareness and underscore the importance of immediate ART initiation, we describe here the pathogenesis, clinical presentation, and impact of treating PHI.