[radioactivist]

While I agree the article doesn't properly contextualize the number, that's not really the right comparison.

Alameda county has had 2564 cases in total since March (up to May 20th) -- so you'd have expected 15 employees to have tested positive for COVID since March. This is a very different statement than 2 of its employees have tested positive shortly after it re-opened.

Loosely one might compare it to those that tested positive in the week of May 20th, which, according to your link, is about 400-500 new cases (about 5x fewer than the cumulative total). So you might reasonably expect something like ~3 cases if you assume the Tesla workers had the same positive test rate as the general population of the county.