Weeks and months after having a confirmed or suspected Covid-19 infection, many people are finding they still haven’t fully recovered. Emerging reports describe lingering symptoms ranging from fatigue and brain-fog to breathlessness and tingling toes. So why does Covid-19 cause lasting health problems? Ian Sample discusses some of the possible explanations with Prof Danny Altmann, and finds out how patients might be helped in the future. Help support our independent journalism at theguardian.com/sciencepod