pathogen

/ˈpæθədʒn̩/

IPA: /P AE1 TH AH0 JH AH0 N/

noun
  1. 1

    Any organism or substance, especially a microorganism, capable of causing disease, such as bacteria, viruses, protozoa or fungi. Microorganisms are not considered to be pathogenic until they have reached a population size that is large enough to cause disease.

Source: https://en.wiktionary.org/wiki/pathogen