Long COVID: Mild infection and sustained long-term complications
Simon Collins, HIV i-Base
Although most COVID-19 studies focus on people hospitalised with severe infection, complications have also been associated with mild infection.
So while many infections have symptoms that resolve within 3 weeks, up to 10% of cases might take more than four weeks and include symptoms that fall short of needing to be hospitalised but by reducing daily activities, challenge the category of being mild.
This was the subject of a BMJ editorial written from experience of a longer mild infection. 
Common symptoms still include fatigue, chest pain and shortness of breath that limit exercise, even in people who were fit before infection and the article stresses the need to measure recovery and time to recovery in greater detail for all stages than just by mortality and time to discharge from hospital.
This is also relevant for the longer recovery times that are already recognised as a complication from more severe stages of COVID-19.
Several UK support groups report having >12,000 members.
The BMJ published a related podcast on post-acute and chronic COVID-19 to support management in primary care. 
A 29-page NIHR review also looks a personal experiences of COVID-19 including the increasing reports of long-term symptoms and how to mange them. 
- Alwan NA. What exactly is mild covid-19? BMJ (28 July 2020).
- Long COVID website
- Body Politic website
- Management of post-acute covid-19 in primary care. BMJ 2020; 370 doi:10.1136/bmj.m3026. (11 August 2020).
- NIHR. Living with COVID-19. (19 October 2020).