in an era when public health slogans abound; wehave had ‘the new public health’, ‘emerging infectiousdiseases’, and now ‘One Health’ joins this lexicon.So, what is ‘One Health’? How does this concept help usthink through, and perhaps solve, public health problems?One Health places disease, particularly infection, in a broadecological context. Many agents of infection target hostsbeyond humans, and One Health seeks to understand andexplain the public health implications of broad host ranges.1One Health is a modern restatement of the old epidemiological triad of host, agent and environment.It has long been known that many infections cross thespecies barriers between humans, domesticated animalsand wildlife. Our view of this has traditionally been somewhat compartmentalised; those who work in food production and regulation are aware of the importance ofSalmonella infections and how modern intensive agriculture, food production, trade and marketing interact to DETERMINE their epidemiology. The more complex interactionsbetween domesticated animals and wildlife that govern thespread of well-known infections such as INFLUENZA, rabies,Ross River and other arbovirus infections, and newlyrecognised infections such as Nipah and Hendra virusinfection still tease expert minds.2There are some specific puzzles. What determines pathogenicity of agents, with species specificity? What, in particular, makes bats an efficient vector of so many newlydescribed infections? How do we determine whether anagent is a true pathogen? What factors determine whether aninfection will cross a species barrier? What measures willmost effectively limit the burden placed on veterinary andhuman health? The solutions to these problems will comeonly from cross-disciplinary work involving epidemiologists, epizootiologists of both wild and domesticated animals, veterinarians, public health practitioners, laboratoryscientists and clinicians.The One Health concept is focused on infectious diseasesand their transmission. However, this is not the only way thathealth can be affected across species. To date, we havefocused LARGELY on animal infection, but microbiological andplant infections also impact health. An example of a crossspecies impact on health was potato blight with its firstimpact directly on plants, and a second impact throughstarvation of humans. Global warming is also predicted tohave an enormous impact on agricultural production (mostof which will not be due to infection), while having asecondary health impact on humans.The One Health concept has largely been the domain ofmicrobiologists and wildlife ecologists. More explorationand discussion of the epidemiological and epizootiologicalbackground is needed to characterise the importance ofthese infections to human and animal public health. Thisspecial edition of the NSW Public Health Bulletin beginsto explore One Health issues of recent or emerging importance in New South Wales. Adamson et al reflect on the levelof coordination that already exists between state health,veterinary and primary industry players, and Dwyer et aldemonstrate how this partnership strengthened the responseto the 2009 influenza pandemic and calls for expansion ofthese collaborative efforts. Hendra virus is a classic exampleof an emerging infectious disease with potentially profoundhuman and animal health consequences, and Hess et alprovide practical management advice while highlightingthe need for a One Health partnership to gain a betterunderstanding of this virus and its ecology. Paterson et alargue that current surveillance systems do not provide characterise new pathogens, to be harnessed for directing human and veterinary public health action. NSW Health staff recently contributed to the first International One Health Congress. Box 1 contains a link to the Congress website where copies of the papers presented are available for further information. Also presented is a glossary to assist the reader with terms that are used in this issue (Box 2). Emerging disease threats demand a team approach that capitalises on the complementary expertise and knowledge of animal and human health professionals. The One Health approach has the potential to improve the lives of all species, whether human or animal.reassurance for early detection and characterisation ofemerging pathogens that present with an ENCEPHALITIS syndrome. Their argument for a standardised algorithm fordiagnostic work up would allow the remarkable developments in virological science, elucidated by WANG, to rapidly