@Pyrrhus, on your time off (just kidding on that one!), I was wondering if you'd been able to determine (just your thoughts) who has the most patients....the U.K. seems to have so many given its size, or the U.S.?
If you're asking about ME patients, standard estimates are that there are roughly 250,000 ME patients in the UK and 1-2 million in the US. But yes, the patients in the UK seem more engaged in the ME/CFS community, for whatever reason.
If you're asking about Long Covid patients, no one knows exactly how many there are because they are difficult to count and there hasn't been a coordinated effort to count them thus far. Hopefully that will soon change!
Hope this helps!