For the last two decades, HIV/AIDS has been held at bay by potent antiviral drugs, aggressive testing and inventive public education campaigns. But the COVID-19 pandemic has caused profound disruptions in almost every aspect of that battle, grounding outreach teams, sharply curtailing testing and diverting critical staff away from laboratories and medical centers. The exact impact of one pandemic on the other is still coming into focus, but preliminary evidence is disturbing experts who have celebrated the enormous strides in HIV treatment.