: difficult in a way that is usually interesting or enjoyable. Thesaurus: All synonyms and antonyms for challenging Nglish: Translation of challenging for Spanish speakers Britannica English: Translation of challenging for Arabic speakers.
To illustrate the tremendous indirect impact of emerging zoonotic diseases on public health policy and structures and on public perception of health risks, the authors provide a number of examples, including that of the Ebola virus, avian influenza, monkeypox and bovine spongiform encephalopathy.
Two major categories of emerging infectionsâ newly emerging and reemerging infectious diseasesâcan be defined, respectively, as diseases that are recognized in the human host for the first time; and diseases that historically have infected humans, but continue to appear in new locations or in drug-resistant forms, or that reappear after apparent control or elimination .