They had one partial positive test result from one random sample taken in March 2019. None of the samples taken during the following months tested positive unti

They had one partial positive test result from one random sample taken in March 2019. None of the samples taken during the following months tested positive until Jan 15, 2020. The paper is a preprint that hasn't been peer reviewed. The overwhelmingly likely explanation is one incorrect test result due to something like an imperfect test or cross contamination. You would need much better evidence than that to rewrite the entire timeline of this disease.