Read on Twitter
NEW—The coronavirus was in the US in mid-December 2019, a few weeks before it was officially identified in China, according to CDC analysis of blood donation samples. This also matches waste water analysis that found virus earlier in Europe. 
#COVID19 https://www.wsj.com/articles/covid-19-likely-in-u-s-in-mid-december-2019-cdc-scientists-report-11606782449
#COVID19 https://www.wsj.com/articles/covid-19-likely-in-u-s-in-mid-december-2019-cdc-scientists-report-11606782449
2) This also matches early indicator data that already found excess flu illnesses in Hubei province (where Wuhan is) in early December as well. https://twitter.com/DrEricDing/status/1333594728672210946
3) here is the earlier waste water study of #SARSCoV2 coronavirus in cities in Northern Italy in mid December already. This matches the reports that it’s been circulating in December before Wuhan outbreak was realized. https://twitter.com/drericding/status/1273941929970020355
4) that said, some think the study might be picking up cross reactivity with other coronaviruses that are seasonally present. I think we need T cell immunity tests coming online soon like @AdaptiveBiotech to be more sure. https://twitter.com/trvrb/status/1333647437869633537
5) CNN also reports it. The study was peer reviewed in a medical journal—not merely a preprint. And it was by CDC scientists. It has some credibility. https://www.cnn.com/world/live-news/coronavirus-pandemic-12-01-20-intl/h_5e4e8b4b5f8f0b44c5286c5f05b483bb
