Joel S. Berson Berson at ATT.NET
Tue Nov 11 23:42:07 UTC 2014

```As explained by others, it's the "degree of separation" -- the first
additional person or persons to become infected (or the person chosen
to be the first in a chain from Kevin Bacon to the ultimate sixth
person in the chain) is separated by one degree from the initial
person infected (or from Kevin).  So the initiator, the first person
to be infected (or Kevin himself) is "patient zero".

See Wikipedia for  various articles titled "Six Degrees of Separation".

Joel

At 11/11/2014 03:07 PM, Dan Goncharoff wrote:

>Is it just me, or does the concept of "patient zero" make little sense when
>the numbering is a time sequence?
>
>The only 'think-around' I see is that, in the sequencing of victims who
>connected to one central source, the central source is considered previous
>to the time sequence, hence the zero.
>
>I myself would have favored a "patient X".
>
>DanG
>
>On Mon, Nov 10, 2014 at 5:28 PM, ADSGarson O'Toole <
>
> > ---------------------- Information from the mail header
> > -----------------------
> > Sender:       American Dialect Society <ADS-L at LISTSERV.UGA.EDU>
> > Subject:      Re: patient zero
> >
> >
> -------------------------------------------------------------------------------
> >
> > Dan Goncharoff
> > > I have always thought about it a 'degrees of separation' from the source.
> > > The source itself has zero degrees of separation.
> >
> > Dan: Originally, the explanation you suggest was the one I thought likely.
> >
> > If you are familiar with Erdos numbers or Bacon numbers then it is
> > natural to hypothesize that "Patient zero" has the number zero for the
> > same reason that Kevin Bacon has a Bacon number of zero. A graph is
> > constructed with links corresponding to "contact" of some kind. For
> > example, the graph to calculate the Bacon number has a direct link
> > between two actors iff they have appeared together in a movie. The
> > graph for the Erdos number has a direct link between two persons iff
> > they have co-authored a paper together. (Complications ensue when
> > individuals have co-written a book and not a paper, etcetera.)
> >
> > The origin node (Erdos or Bacon) is assigned the number zero, and the
> > other nodes in the graph are labeled with the minimum distance from
> > the origin node measured by link traversals. Here is an article
> > stating that Kevin Bacon has a Bacon number 0.
> >
> > Title: The Six Degrees of Kevin Bacon
> > Author: Stephanie Blanda
> > Date: November 22, 2013
> >
> >
> > [Begin excerpt]
> > While there is only one person with Bacon number 0 (Kevin Bacon
> > himself), most individuals involved in the Hollywood film industry
> > have a Bacon number of 6 or less.
> > [End excerpt]
> >
> > Does this explain why "patient zero" was assigned the number zero?
> > Perhaps not. Look at this Wikipedia article that apparently shows the
> > scientific paper with the graph for "patient zero". The numbers do not
> > correspond to distance or link traversals:
> >
> > http://en.wikipedia.org/wiki/Index_case
> >
> > Garson
> >
> > ------------------------------------------------------------
> > The American Dialect Society - http://www.americandialect.org
> >
>
>------------------------------------------------------------
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```