More than 70 % of SARS-COV-2 recorded infections were contracted from undocumented cases of the disease .
However , an epidemiological model of the beginning of the outbreak in China ( published in Science ) suggested that `` pre-symptomatic shedding may be typical among documented infections '' and `` undocumented infections were the infection source for 79 % of documented cases '' .
Severe acute respiratory syndrome coronavirus 2