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Line breaks: in|fec¦tious
Pronunciation: /ɪnˈfɛkʃəs

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
More example sentences
  • However, conjunctivitis caused by the common cold is very infectious and can spread rapidly between people.
  • Severe acute respiratory syndrome is highly infectious and potentially lethal.
  • Glandular fever is an infectious illness that causes swelling of the lymph nodes.
1.1Liable to spread infection: the dogs may still be infectious
More example sentences
  • 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.
  • By the way, colds spread through touching infectious surfaces or inhaling viruses.
poisonous, toxic, noxious
2Likely to spread or influence others in a rapid manner: a loud infectious laugh her enthusiasm is infectious
More example sentences
  • 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.
  • 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.


On the differences in meaning between infectious and contagious, see contagious (usage).



Example sentences
  • At the same time, a European-derived painting style called Neo-Expressionism proved to be infectiously popular amongst the Art Institute students.
  • Though markedly different, both have strong elements of dance, which had the conductor almost pirouetting on the rostrum, thus coaxing infectiously springing rhythms from his colleagues.
  • Churchill's infectiously ebullient personality had served his government and his country well in the First World War as well as the Second.


Example sentences
  • An overwhelming majority of persons living with HIV infection do not get detected and remain unknowing of their potential illness and infectiousness to others.
  • If one takes these vibrios and cultivates them on nutritional media in the lab, or uses them to infect animal models, their infectiousness declines rapidly.
  • Perhaps this is why the film is best seen in a crowded theatre, where the infectiousness of cathartic emotion can have full play.

Definition of infectious in:

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