This example for instance fits me perfectly.
"Given that the immune cells generate
oxidative stress to kill pathogens, it’s no surprise that oxidative stress would be increased in acute COVID infections. SARS-CoV-2, though, comes with a special twist: when it enters the
ACE-2 receptor by elevating Ang II levels, it produces mitochondrial dysfunction and accumulations of the superoxide radical and other oxygen and nitrogen species.
With over a dozen studies finding a redox imbalance in ME/CFS, high levels of oxidative/nitrosative stress may be the most consistent finding in all of ME/CFS. Interestingly, levels of oxidative/nitrosative stress rise to particularly high peaks after exercise in ME/CFS. Metabolomic studies indirectly suggest the presence of high levels of oxidative stress.
A variety of studies have also found high levels of pro-oxidants – chemicals that either directly produce oxidative stress or impair antioxidant levels – in both ME/CFS and COVID. They include ferritin, free iron, homocysteine, neutrophil extracellular traps,
altered levels of nitric oxide and hydrogen sulfide (in COVID), and
altered tryptophan metabolism."
https://www.healthrising.org/blog/2021/08/21/free-radicals-chronic-fatigue-syndrome-long-covid-pasc/