資料來源:
1. Scientific American:
https://www.scientificamerican.com/article/how-dangerous-is-the-delta-variant-and-will-it-cause-a-covid-surge-in-the-u-s/
2. NBC news:
https://www.nbcnews.com/science/science-news/delta-delta-variants-everything-need-know-rcna1281
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