What is behind the lingering effects for some people who contracted COVID-19?

“UCLA Health among 8 sites enrolling volunteers who have been tested for COVID-19, to track long-term health effects of the virus” (UCLA Health Blog, 2/18/21).

https://connect.uclahealth.org/2021/02/18/what-is-behind-the-lingering-effects-for-some-people-who-contracted-covid-19/