A Brazilian man who last summer had no evidence of remaining HIV after more than a year off antiretroviral treatment once again had a detectable viral load a few months later. As part of a clinical trial, the São Paulo man, who had stable viral suppression, added two more antiretrovirals (dolutegravir and maraviroc) to his three-drug regimen along with nicotinamide, a form of niacin (vitamin B-3) for 48 weeks. In March 2019, he started a closely monitored treatment interruption. More than 15 months later, he still had undetectable HIV RNA and HIV DNA, and his HIV antibodies fell to a very low level. But in September 2020, the man was diagnosed with secondary syphilis; two months later, his viral load exceeded 6,300 and his HIV antibodies started to rise. He resumed treatment, and his viral load again became undetectable. The emerging HIV strain had substantial genetic differences from the original strain. Further analysis is underway to determine whether this is a case of viral rebound or reinfection.