[enzo1982]

These 320k tests were performed in the Guangdong province which has a population of 113 million and ~10,000 confirmed COVID-19 cases, or about 0.009% of the population.

If they found a 0.5% positive rate on background tests there, that would suggest the real number of cases to be hundreds of thousands in that province alone.

You seem to be referring to this report: https://www.statnews.com/2020/02/25/new-data-from-china-butt...

That article suggests that the 320,000 tests were not a background test, but they tested "worried people [who] flooded fever clinics to be tested". Actual numbers across all population would hopefully be much less than 0.5%.

The article also states "The claim [that there's not huge transmission beyond what you can see clinically] was quickly challenged by an infectious diseases expert who serves on a committee that advises the WHO's health emergencies program.".