To know something, we must define it.

There has been much enthusiasm in some Covid-affinity corners for the prevalence and seriousness of "long-Covid."  The claim is that there are myriad post-Covid afflictions which are due to the Covid infection and which persist either for a long time or permanently depending on your catechism.  

As the evidence against the efficacy of vaccines, mandates, vaccine passports, lock-downs and masking rises, so seems to rise the conviction in long Covid.  

We are still only two and a half years into Covid so while much has been learned, there is much still not understood.  It feels like the early days of prior moral and health panics over Chronic Lyme Disease, Chronic Fatigue Syndrome, and Herpes Simplex.  All of which are to some extent real but none of which are as serious as the initial panicky claims regarding prevalence, seriousness and impact.  

Long Covid may or may not be real, may or may not be widely prevalent, and may or may not have a serious impact on individuals.  Right now, we don't know.  All the early research I have seen has been laughably inadequate in terms of population size, randomization, controls, methodological rigor, etc.

As is often the case when there is a moral and health panic, our understanding is afflicted by inadequate definitions about what exactly we are discussing.  From LongCovid: Can it be avoided? by Vinay Prasad.  He has other pertinent observations but I liked this.

First a definition. Mine has two parts.

Long covid is a collection of symptoms and problems after covid (1) beyond a similar level of illness from a different respiratory virus. Prolonged convalescence has always happened for some people after a respiratory virus, particularly among those who wind up in the intensive care unit, but long covid implies there is something unique to this virus. And long covid are these signs and symptoms that occur beyond comparable illness from other virus, (2) when you test people equally. If you do more scans, you will find more abnormalities, so long covid must be findings beyond the equivalent level of surveillance post (other) respiratory infection.

If we accept this 2 part definition, we must concede that the current long-covid literature is in its infancy. We shall someday see how much long covid fits. Perhaps all we know with confidence at this moment is that anosmia is part of this.

That is a useful and workable definition.  But of course, any definition will do.  There just has to be one.  All epistemology, all knowledge begins with definitions.