Definition of patient zero in English:

patient zero

noun

US
  • usually in singular Used to refer to the person identified as the first carrier of a communicable disease in an outbreak of related cases.

    ‘patient zero for the outbreak was suspected to be a 2-year-old boy’
    Compare with index case
    ‘epidemiologists know who Patient Zero is, and they have him in isolation’
    figurative ‘she was patient zero in a cyberbullying epidemic’
    • ‘Part of the reason that we went to this area and identified patient zero was because when you start to look at the origins, where this all started, you might get some clues and learn some lessons.’
    • ‘They have found patient zero, apparently the first case of swine flu now identified at a hog farm in Peratti, Mexico.’
    • ‘How exactly that jump happened and what it meant in terms of human-to-human transmission still is not entirely clear, although once you start locating this Patient Zero and some of the earliest patients, you can look.’
    • ‘With meningitis outbreaks, he said, there is no "patient zero."’
    • ‘If you understood viruses better you would understand that 'patient zero' usually has a strong immunity to the virus if they aren't completely immune.’
    • ‘The "patient zero" behind the announcement in New York has suggested that his initial HIV infection occurred in late October 2004.’
    • ‘The GP suspected she had the virus and sent her by ambulance to Tan Tock Seng Hospital, which confirmed her as Singapore's Patient Zero.’
    • ‘It will help MSF efforts to identify the outbreak's patient zero - and hence where the Ebola outbreak originated.’
    • ‘Patient Zero was a grandmother in New Delhi whose lungs filled up with fluid from trying to fight the flu.’
    • ‘As any parent of schoolgoing kids knows, headlice outbreaks are fairly common, and targeting Patient Zero is usually impossible.’