Definition of infectious in English:



  • 1(of a disease or disease-causing organism) liable to be transmitted to people, organisms, etc. through the environment.

    ‘outbreaks of infectious diseases’
    ‘was polyneuritis infectious?’
    ‘a highly infectious virus’
    • ‘He was taken to the infectious diseases hospital three days later.’
    • ‘The classic means of protecting persons exposed to infectious diseases is vaccination.’
    • ‘Against this background, the emergence of new human infectious diseases or viruses is unsurprising.’
    • ‘This cross sectional survey was not designed to provide direct evidence of transmission of infectious diseases in prison.’
    • ‘Bone lesions from infectious disease or parasitic infection are rare.’
    • ‘Measles is highly infectious and could spread very quickly.’
    • ‘Mumps is highly infectious and spreads rapidly in susceptible people living in close proximity.’
    • ‘MPs poured out of the Commons potentially spreading any infectious agent.’
    • ‘There are also some major infectious diseases for which vaccinations have not been developed.’
    • ‘What if I tell myself the rash will go away and it becomes infectious and spreads even further?’
    • ‘Must my rejected bag secretly be destroyed to prevent the spread of infectious agents?’
    • ‘Glandular fever is an infectious illness that causes swelling of the lymph nodes.’
    • ‘Molecular biology has had a major impact on medical microbiology and infectious disease.’
    • ‘Clean bathroom surfaces also help prevent the spread of infectious germs.’
    • ‘Severe acute respiratory syndrome is highly infectious and potentially lethal.’
    • ‘However, conjunctivitis caused by the common cold is very infectious and can spread rapidly between people.’
    • ‘However, the bacteria are not as infectious as the common cold and cannot be spread by casual contact.’
    • ‘Unravelling the genetic and environmental determinants of infectious disease will soon be feasible.’
    • ‘It was thought that close contact with an infected person was needed for the infectious agent to spread from one person to another.’
    • ‘Lyme disease is an infectious illness caused by the bacterium Borrelia burgdorferi.’
    • ‘Our feeling, however, is that they most likely contain a single infectious capsid.’
    • ‘The cull of a flock of 9,000 pheasants was under way yesterday after confirmation of a highly infectious bird disease.’
    contagious, communicable, transmittable, transmissible, transferable, conveyable, spreadable, spreading
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    1. 1.1 Liable to spread infection.
      ‘the dogs may still be infectious’
      • ‘Dutch botanist Martinus Bijerinck called this infectious fluid contagium vivum fluidum.’
      • ‘She was misdiagnosed with gastro-enteritis, and transferred to Castle Hill because it was felt she was infectious.’
      • ‘A person with glandular fever is most infectious when they have a fever (high temperature).’
      • ‘By the way, colds spread through touching infectious surfaces or inhaling viruses.’
      • ‘Those treated can support their families and are likely to be less infectious.’
      • ‘Some of the cheapest meat is stripped by machines and high-pressure jets from the bone, which is likely to be highly infectious in a sick cow.’
      contaminating, germ-laden, polluting, pestilential, virulent
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  • 2Likely to spread or influence others in a rapid manner.

    ‘a loud infectious laugh’
    ‘her enthusiasm is infectious’
    • ‘His quick wit and absolutely infectious laugh are almost as entertaining as the show itself.’
    • ‘She had a warm personality combined with a loud infectious laugh.’
    • ‘Neville Garden communicated his own infectious enthusiasm, week after week for many years, through his work as a critic.’
    • ‘The balance of chilly remove and infectious abandon that Morton conveys adds much to Morvern's allure.’
    • ‘Seeing Chris thrashing around his drum kit made Steven smile and the infectious smile spread to Donnie.’
    • ‘Poverty is something that is contagious and infectious in our community.’
    • ‘Valencians don't simply watch fireworks - they almost commune with them and the feeling is infectious.’
    • ‘Darlene simply had the kind of infectious positive attitude that influenced everyone in her presence.’
    • ‘Long had he been plagued by an infectious fear of spreading weakness in times that demanded strength.’
    • ‘A most pleasant man, his naturally friendly manner and infectious good humour have made him a popular member of the Ship's Company.’
    • ‘Your enthusiasm is infectious; it spreads as rapidly through conversations as it does through bloodlines.’
    • ‘He grinned slowly, an infectious smile that soon spread, spanning ear to ear.’
    • ‘Nevertheless, she understands the essence of the formula, and applies it in a manner that is infectious.’
    • ‘The dog had an infectious energy, a boisterous nature, that spread wherever he bounded.’
    • ‘He had a wonderful sense of humour and an infectious, hearty laugh.’
    • ‘It does make you an energetic person, and one who has an infectious and personable manner.’
    • ‘The author's enthusiasm and infectious desire to communicate his ideas comes across loud and clear.’
    • ‘His infectious enthusiasm for technology is spread through his weblog.’
    • ‘Not only that, but it's the infectious happiness of the manner, with the very sterile, factual detailing of demise that is the content.’
    • ‘The problem is once you fall for the guy with the infectious laugh or the girl that takes your breath away, you have to get them to notice you.’
    irresistible, compelling
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On the differences in meaning between infectious and contagious, see contagious