Long Covid is not medically definitive, but a term that describes a portion of the population struggling with symptoms for weeks or months after being infected with Covid-19, and not just those who were seriously ill. In fact, there is no evidence that links severity of infection and ongoing symptoms like fatigue. Data from the app-based Covid-19 symptom study, being conducted in real time by the genetic epidemiology team at King’s College London (KCL), showed that up to 60,000 people had reported having symptoms for more than three months. Fatigue is the most common, but breathlessness, chest tightness, brain fog, gastrointestinal issues, joint pain, headaches and vertigo are among other reported manifestations, ranging from mild to debilitating. For many, the psychological effects are profound.

What is causing so many people to be knocked sideways like this? Preliminary data from the first study to assess the long-term impact of Covid-19 on multiple organ health in “low-risk” individuals (those who are relatively young and healthy) with ongoing symptoms shows 70% of the first 200 screened patients have impairments in one or more organs, including the heart, lungs, pancreas and liver, four months after they were first ill.

More data is needed, but an emerging theory regarding the ongoing fatigue people are experiencing is that long Covid could be a post-viral syndrome akin to chronic fatigue syndrome (CFS). In fact, Professor Frances Williams, who is part of the genetic epidemiology team at KCL overseeing the app study, and who has been researching CFS for decades, believes Covid-19 may “finally unlock the black box of chronic fatigue, which is, truly, one of the last frontiers in medicine.”