The use of the term “emerging” implies something new and threatening to human kind, either arising de novo or of an agent unexpectedly coming to our attention from a previously unknown source or with hitherto unrecognised characteristics. Indeed several new agents have caused serious harm, both in terms of mortality and morbidity as well as economic loss. It is for these reasons that emerging infectious diseases of humans and animals are of mounting concern to public health officials and infectious disease specialists alike. Since the early 1990’s, the term has come to embrace in its loosest sense those diseases that were hitherto unknown infections that have been considered as under control, only to re-emerge in a new geographical location or with renewed vigour, or both. Many until recently have been the preserve of those specialists with a particular interest in tropical or veterinary diseases, rarely coming into the consciousness of clinicians or microbiologists in the developed world apart from isolated, imported cases. All this has......