They are the latest in a series of people with HIV who appear to be practically rid of the virus – although researchers warn it is too soon to declare them cured. Earlier this year, reports emerged of an infant and a group of 14 adults who all experienced functional HIV cures, meaning that although their bodies still had traces of the virus, it was no longer active.

So far, these functional cures have all been attributed to very early treatment with antiretroviral drugs, before the virus could take hold. The Boston patients, in contrast, are free of the virus thanks to a combination of a bone marrow transplant plus continuing antiretroviral drugs to stop newly donated immune cells from being infected.