evidence: Researchers also found that the VB variant impacted the rate of CD4 cell decline in infected individuals—this cell decline is the "hallmark" of damage to the immune system caused by HIV, the press release says. CD4 cells, also known as T-cells, are infection-fighting white blood cells, according to the US National Library of Medicine. HIV attacks and destroys these CD4 cells—and when too many of the cells are lost, the body has trouble fighting off infections. Very low CD4 counts are indicative of acquired immunodeficiency syndrome (AIDS). The study showed that the VB variant caused infected people's CD4 counts to drop twice as fast as other HIV strains, meaning they were at risk of developing AIDS more quickly. Without treatment, researchers estimated a person with the VB variant would develop AIDS two to three years after diagnosis, compared to six to seven years for people with a different HIV strain. Despite the VB variant's increased severity and transmissibility, researchers found that the variant responded to current HIV treatments (like antiretroviral drugs) as well as other strains do. Survival rates after starting treatment were also similar among those with the VB variant and other variants. How (And Why) Do Variants Emerge?