patient zero

Contact tracing for people who test positive to SARS-COV-2 involves stepping back through a network of people to find the original source of the disease. All pathways lead to this person who is patient zero. The concept is relative.  Patient zero on the Ruby Princess is thought to be someone working in the kitchen.  Patient zero for Greece is thought to be someone who attended the Milan Fashion Week. Patient zero for the world could be someone at the wet market in Wuhan who came into contact with an animal infected with the virus.  This is all uncertain because it is not always possible to identify the person who introduced the disease.  Of course the conspiracy theorists have their own ideas about who patient zero is, usually targeting a person who fits in with their political leanings.