The Rules of Contagion: Why Things Spread - and Why They Stop

by Adam Kucharski

Take the 2009 ‘swine flu’ pandemic. The outbreak started when genes from four viruses – a bird flu virus, a human flu virus and two different swine flu strains – jumbled together inside an infected pig in Mexico, creating a new hybrid virus that then spread among humans.

In 2013, for example, The Times reported that Prince William had Indian ancestry, after testing two distant cousins on his mother’s side. Genetics researchers soon criticised the story, because it had revealed personal information about the prince without his consent.