Is Ula Kana an allegory for COVID? Nope. Although...
In Lava Red Feather Blue, Merrick awakens Larkin (and the destructive faery Ula Kana) in March 2020, unleashing all kinds of mayhem on his country. Given the date, you might wonder: does Ula Kana represent COVID-19?
The short and obvious answer is no, I didn't intend that, nor could I have, given I wrote the entire thing before anyone had heard of COVID. I set the timing as the current year (that is, the year it was during the editing phase) so that it wouldn't seem too dated; end of story. HOWEVER...
I'm fine with retrospective reinterpretations. And if asked, I generally say the fae represent nature, and the fae-human conflicts and harmonies represent our complicated but vital relationship with the rest of the natural world. And what is a dangerous virus if not a particularly nasty piece of the natural world?
So, though I didn't intend it: sure, you could make a case for Ula Kana being the 'rona. But it was through coincidence, not design.
(Eidolonia does not, as far as we know, have an actual COVID outbreak. They don't have a lot of contact with the rest of the world, not to mention they have magic. They get enchantment-related illnesses, which are nasty, but my firm belief is they'd obliterate regular infectious diseases in no time flat.)