As COVID-19 sweeps through the world, medical scientists are racing to find the origin of the outbreak, specifically, to locate patient zero of the disease.

However, scientists said it is extremely difficult to find patient zero of a contagious disease. Scientists have yet to find patient zero for the 1918 influenza pandemic, HIV or the H1N1 influenza in 2009.

Voiceover: Ian Goodrum

Script: Ma Chi

Editing: Zhang Chunyun, Shan Juan