Do Scarce Targets or T Killers Control Primary HIV Infection?

Early in HIV infection, a million virions per milliliter appear in the blood; yet over the next few weeks, this number drops by two orders-of-magnitude. Symptoms resolve and a quasi-steady-state forms. What halts the viremic outburst? In 1996, Phillips proposed a simple explanation: HIV depletes its target cells. Here, we combine observations of primary disease with mathematical analysis to argue that target-cell scarcity cannot explain the virusʹs decline, indirectly shoring up the chief alternative theory: control by the immune system.