I have had trouble finding one as well (the parent comment).

austincheney · on March 11, 2020

I found this article which claims The WHO's use of the term is arbitrary based upon the conditions at hand.

https://www.theverge.com/2020/3/11/21156325/coronavirus-pand...

I suspect The WHO declared this a pandemic, based upon the article, out of concern for what they perceive to be insufficient government activity.

concerned_user · on March 11, 2020

As I said there is probably no official WHO definition or criteria due to big economic impact of such declaration and it is decided on a case by case basis.

EDIT: I was wrong, here is the chart: https://www.who.int/influenza/resources/documents/pandemic_p...