Millions of people around the world have been left managing the complex and amorphous syndrome that is long COVID. But the underlying cause of this myriad of symptoms is not clear. One hypothesis is that the virus is able to find a safe haven in the body from which it can bide its time and potentially re-emerge - a viral reservoir. Now researchers studying long COVID have found evidence of SARS-CoV-2 in a series of organs around the body, most notably the gut, months after the infection appears to have been cleared from the respiratory system. While there is still a long way to go before the reservoir hypothesis can be confirmed, these data provide compelling new support for the theory. In this episode of Coronapod, we discuss how the studies were carried out, why the question of long COVID's cause is so difficult to crack, and what more needs to be done to get a firm answer.News: Coronavirus ‘ghosts’ found lingering in the gutSubscribe to Nature Briefing, an unmissable daily round-up of science news, opinion and analysis free in your inbox every weekday. See acast.com/privacy for privacy and opt-out information.