Prevalence 

Covid-19 is now recognised as a multi-organ disease. Roughly one in five people who test positive experience symptoms for four weeks or more. The development of long-Covid – where symptoms last weeks or months after the infection has gone – is not predicted by initial Covid-19 severity and the burden of illness includes many people who had mild to moderate infections. Pre-existing conditions such as heart or lung disease are also likely to be aggravated in patients who had severe disease and were hospitalised. 

It is thought that asymptomatic patients may also develop long-Covid, but this is currently less clear. Patients of all ages are affected and there is growing evidence of long-Covid in children. Covid-19 is still a relatively new disease and research continues to generate new evidence at a rapid rate. This module reflects the situation in April 2021.