Risk factors for human disease emergence

TLDR

A review of 1,415 human‑pathogenic organisms shows that 61% are zoonotic and 175 species are classified as emerging diseases. The study tests whether zoonotic pathogens are more likely to be associated with emerging diseases than non‑zoonotic ones. The analysis found that 75% of emerging pathogens are zoonotic, making zoonotic organisms twice as likely to cause emerging diseases, with protozoa and viruses especially prone and helminths unlikely, while transmission route showed no association, marking the first quantitative risk‑factor study.

Abstract

A comprehensive literature review identifies 1415 species of infectious organism known to be pathogenic to humans, including 217 viruses and prions, 538 bacteria and rickettsia, 307 fungi, 66 protozoa and 287 helminths. Out of these, 868 (61%) are zoonotic, that is, they can be transmitted between humans and animals, and 175 pathogenic species are associated with diseases considered to be ‘emerging’. We test the hypothesis that zoonotic pathogens are more likely to be associated with emerging diseases than non–emerging ones. Out of the emerging pathogens, 132 (75%) are zoonotic, and overall, zoonotic pathogens are twice as likely to be associated with emerging diseases than non–zoonotic pathogens. However, the result varies among taxa, with protozoa and viruses particularly likely to emerge, and helminths particularly unlikely to do so, irrespective of their zoonotic status. No association between transmission route and emergence was found. This study represents the first quantitative analysis identifying risk factors for human disease emergence.