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’
    • ‘It was thought that close contact with an infected person was needed for the infectious agent to spread from one person to another.’
    • ‘There are also some major infectious diseases for which vaccinations have not been developed.’
    • ‘Severe acute respiratory syndrome is highly infectious and potentially lethal.’
    • ‘He was taken to the infectious diseases hospital three days later.’
    • ‘Glandular fever is an infectious illness that causes swelling of the lymph nodes.’
    • ‘Clean bathroom surfaces also help prevent the spread of infectious germs.’
    • ‘Molecular biology has had a major impact on medical microbiology and infectious disease.’
    • ‘However, conjunctivitis caused by the common cold is very infectious and can spread rapidly between people.’
    • ‘MPs poured out of the Commons potentially spreading any infectious agent.’
    • ‘This cross sectional survey was not designed to provide direct evidence of transmission of infectious diseases in prison.’
    • ‘The classic means of protecting persons exposed to infectious diseases is vaccination.’
    • ‘The cull of a flock of 9,000 pheasants was under way yesterday after confirmation of a highly infectious bird disease.’
    • ‘Lyme disease is an infectious illness caused by the bacterium Borrelia burgdorferi.’
    • ‘Unravelling the genetic and environmental determinants of infectious disease will soon be feasible.’
    • ‘Bone lesions from infectious disease or parasitic infection are rare.’
    • ‘Our feeling, however, is that they most likely contain a single infectious capsid.’
    • ‘Mumps is highly infectious and spreads rapidly in susceptible people living in close proximity.’
    • ‘Against this background, the emergence of new human infectious diseases or viruses is unsurprising.’
    • ‘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?’
    • ‘Measles is highly infectious and could spread very quickly.’
    • ‘However, the bacteria are not as infectious as the common cold and cannot be spread by casual contact.’
    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’
      • ‘She was misdiagnosed with gastro-enteritis, and transferred to Castle Hill because it was felt she was infectious.’
      • ‘Those treated can support their families and are likely to be less 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.’
      • ‘Dutch botanist Martinus Bijerinck called this infectious fluid contagium vivum fluidum.’
      • ‘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’
    • ‘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.’
    • ‘She had a warm personality combined with a loud infectious laugh.’
    • ‘It does make you an energetic person, and one who has an infectious and personable manner.’
    • ‘Seeing Chris thrashing around his drum kit made Steven smile and the infectious smile spread to Donnie.’
    • ‘Not only that, but it's the infectious happiness of the manner, with the very sterile, factual detailing of demise that is the content.’
    • ‘Your enthusiasm is infectious; it spreads as rapidly through conversations as it does through bloodlines.’
    • ‘The balance of chilly remove and infectious abandon that Morton conveys adds much to Morvern's allure.’
    • ‘Long had he been plagued by an infectious fear of spreading weakness in times that demanded strength.’
    • ‘He had a wonderful sense of humour and an infectious, hearty laugh.’
    • ‘Darlene simply had the kind of infectious positive attitude that influenced everyone in her presence.’
    • ‘His infectious enthusiasm for technology is spread through his weblog.’
    • ‘The author's enthusiasm and infectious desire to communicate his ideas comes across loud and clear.’
    • ‘His quick wit and absolutely infectious laugh are almost as entertaining as the show itself.’
    • ‘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.’
    • ‘Neville Garden communicated his own infectious enthusiasm, week after week for many years, through his work as a critic.’
    • ‘A most pleasant man, his naturally friendly manner and infectious good humour have made him a popular member of the Ship's Company.’
    • ‘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.’
    • ‘The dog had an infectious energy, a boisterous nature, that spread wherever he bounded.’
    irresistible, compelling
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On the differences in meaning between infectious and contagious, see contagious