01 May 2020 Vol 368, Issue 6490
Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV-2)
By Ruiyun Li, Sen Pei, Bin Chen, Yimeng Song, Tao Zhang, Wan Yang, Jeffrey Shaman
Science01 May 2020 : 489-493 Open Access CCBY
Prior to travel restrictions, most SARS-CoV-2 infections went undocumented and substantially contributed to global virus spread.