Thread by @Friedemann1

Meta-analyses and studies of large cohorts have shown that around 20–40% of individuals infected with SARS-CoV-2 have asymptomatic disease

1/
nature.com/articles/s4157…

The complexities of a working definition for the term ‘asymptomatic’ in this disease are exemplified by an early report from Wuhan, which showed that about one-third of individuals with asymptomatic infections had lung changes that were visible on computed tomography scans
2/

...subsequently confirmed in several other studies. That is, end organ damage can ensue in individuals who were otherwise unaware of their infection.
3/

individuals with symptomatic and asymptomatic infections have a comparable viral load, supporting the idea of a similar potential for transmission, although virus clearance may be faster in asymptomatic infections, which suggests a shorter period of transmission
4/

Long COVID is estimated to ensue from about 20% of symptomatic infections
One study estimated that one-third of cases of long COVID ensue from asymptomatic acute infection events.
5/

The debate regarding this risk has underpinned strategies for moving out of lockdowns and learning to ‘live with the virus’. Particularly in countries with high levels of vaccination, there is a view that the link between infection and severe outcome has been weakened
6/

The UK is currently experiencing a wave of a considerable number of new infections per day with the Delta variant but, compared with previous waves of infection, a low translation of these numbers into acute hospital admissions and fatalities.
7/

A key question is...these milder or asymptomatic infections could contribute to a future long-term disease burden of long COVID. ...predicted tolerance for 25,000 new infections per day could translate into ...about 5,000 individuals per day who will develop long COVID
8/

Asymptomatic infection can...prime immune memory, but...potential...yet undefined, risk of long COVID
...argument against any complacency regarding a...future as a population with low-level asymptomatic carriage is...ongoing transmission and..fuelling future variants of concern