Human and animal influenza surveillance: Ecologic and evolutionary insights, pandemic preparedness, and the One Health Initiative

Rapid evolution of influenza A viruses and increasing interactions between humans and animals poses public health threats to all affected species. Although influenza originates and is maintained in wild migratory birds, intra- and inter-species transmissions, for example to domestic birds, mammals, and humans, have occurred globally and create opportunities for novel genotypes to emerge with pandemic potential.

The One Health Initiative is a global strategy aimed at understanding all aspects of healthcare for humans, animals, and the environment through multidisciplinary collaboration and underlies many influenza pandemic preparedness plans and disease control efforts. Despite expansive surveillance efforts, many threats continue to be recognized only after human infection (i.e. swine-origin H1N1pdm and avian H7N9 outbreaks). This is largely attributed to haphazard and opportunistic outbreak surveillance. Research efforts focused on the human-animal interface repeatedly missed viral transmission events between domestic and wild animals. All currently circulating influenza strains with pandemic potential were generated through a complex history of genetic exchange between viruses circulating in wild and domestic hosts. The result is an incomplete understanding of how ecological and epidemiological processes shape influenza’s dynamically evolving gene pools.

Nevertheless, global increase of influenza surveillance efforts, coupled with molecular and bioinformatics advancements have revealed influenza transmission within and between large-scale ecological systems create ideal circumstances for novel pathogen emergence. We review the evolutionary and epidemiological insights generated from analyses of available surveillance data of humans, wild and domestic animals, highlight research gaps, and propose future directions for hypothesis-driven surveillance and risk assessment of circulating viral threats.