* What is the measure of disease severity?
* Is there a correlation between measures of disease severity and anosmia in Covid-19?
* Is there a correlation between disease severity of other viruses that trigger chronic fatigue symptoms and incidences of CFS?
The anosmia question seems relevant if we assume that the virus damages the nervous system.
Be very careful with how you phrase that. Fatigue is very much a physical thing, not psychological. It's just that medically, we have no way to quantify it, so it doesn't show up easily in lab tests. That does NOT mean it doesn't exist, or that it only exists in the head. (edit: and before someone says "lactate", keep in mind that that only measures muscle strain, one of the few forms of fatigue that we do know how to measure)
How people experience fatigue has a psychological component, but saying to someone who has been fatigued for years that their issues are predominantly psychological is very dismissive. Odds are they've been hearing that from their physicians for a long time already.
[edit] To downvoters, consider that the placebo effect is incredibly strong, much stronger than you give it credit for most likely, and has gotten stronger over time as our faith in medicine has.
A 2014 study showed that placebo was 50% as effective as real migraine medication in treating pain after migraines [1].
Similarly for the nocebo effect. A study showed that 20% of people getting placebo drugs in a clinical trial developed side-effects. The nocebo effect may be even stronger than placebo. [2,3].
I'm not minimizing COVID and I'm not saying these people are "making it up." I'm saying, humans aren't computers, and human viruses aren't computer viruses. It's not a case of X happens to you and the result is deterministically Y. There's a lot more to your subjective experience. Generally the more strongly you believe in a potential range of outcomes, the more likely you are to, basically, get them. COVID anxiety is huge, and some of these "long-haulers" symptoms could easily be nocebo.
If this long-haul syndrome really is nocebo, it opens up potential avenues for treatment.
We need to keep an open mind.
[1] https://www.health.harvard.edu/mental-health/the-power-of-th...
[2] https://www.health.harvard.edu/newsletter_article/The_nocebo...
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4804316/