Fig. 4.

Emerging pathogens such as zoonoses (black arrows) and resistant bacteria (gray arrows) illustrate interdependencies generated by gene flow among the economic sectors of food, health and the environment. In zoonoses, vertebrates such as birds act as reservoirs for pathogens that can infect humans. Through direct transmission or via domesticated animals, zoonoses are passed to humans and cause regular local and rare global epidemics (such as the flu outbreaks of H5N1-2004 and H1N1-2009). ‘Reverse zoonoses’ are transmitted from infected humans to wildlife (179). Antimicrobial resistance in bacterial stains associated with livestock evolves in response to widespread use of antibiotics in agriculture and to a lesser degree due to treatment in humans. Via food items, industry workers and waste disposal, resistant strains enter other human contexts. In a public health context resistant strains constitute a growing extra risk during treatment of illnesses, e.g., in hospitals. Antibiotics in human effluent cause widespread resistance selection in natural and semi-natural environments, which together with resistance reservoirs in natural environments further increase the risks of resistant pathogens in humans. In the figure, the dashed line indicates a variety of poorly known interactions among wild species.