The ‘One Health’ Paradigm: Time for Infectious Diseases Clinicians to Take Note?

What do severe acute respiratory syndrome (SARS), monkeypox, highly pathogenic influenza A, new variant Creutzfeld-Jacob disease, cryptosporidiosis and verotoxigenic Escherichia coli have in common? All represent infectious diseases that have emerged, been recognized or changed their distribution markedly over the past three decades, and all may be considered to be ‘zoonotic’ threats; ie, they are diseases (or commensal microbes) found in animals that can be transmitted to humans, causing disease in the latter. The preponderance of zoonoses among emerging infectious diseases is striking: a pre-SARS Institute of Medicine (USA) report (1) suggested that approximately three-quarters of emerging infections originated in animals. Zoonotic threats become an even greater menace when combined with the rapidity of air travel, and the high volumes of animal trafficking and smuggling that currently occur. SARS was an infectious threat that moved from a natural reservoir (likely bats) to civet cats in animal markets in Guangdong province, China, and were then carried by infected humans to the hospitals of Toronto, Ontario, in a few short months (2). Similarly, an Old World virus causing West Nile virus fever and encephalitis emerged as a novel infectious entity in the western hemisphere in 1999, possibly following illicit animal importation into New York (USA) (3,4). The list goes on.