Unlikely this was COVID, we know enough about how it spread to almost certainly rule out it was outside China in significant enough numbers for you to have had

Unlikely this was COVID, we know enough about how it spread to almost certainly rule out it was outside China in significant enough numbers for you to have had it in Japan before 2020. The May paper is most likely wrong. You heard about it because it is an extraordinary claim that gets attention, not because the evidence is good.