Researchers have discovered that a new group of T-cells, called T memory stem cells, are susceptible to HIV and likely represent the longest-lasting cellular niche for the virus.” HIV’s devastating impact on the human immune system is due to its habit of infecting the CD4-positive T-cells that direct and support the infection-fighting activities of other immune cells. Subtypes of CD4 T-cells have different functions and all are capable of being infected by HIV. With antiviral treatment, drugs keep the virus in infected cells from replicating; because most CD4 T-cells are short-lived, they die relatively soon. CD4 T memory stem cells, however, can live for decades, and give rise to several types of T-cells. This means HIV-infected T memory stem cells could continuously regenerate new HIV-infected cells, fueling HIV persistence in the body.