Full text full text is available as a scanned copy of the original print version get a printable copy pdf file of the complete article 196k or click on a page image below to browse page by page. This is a pdf only article the first page of the pdf of this article appears above. Certainly as insecticides urban development and sanitation increase our isolation from nature the risk of sporadic infection grows and the maintenance of our immune state is rapidly becoming as important as but more difficult than the supply of clean water hardly any vaccine has yet been introduced without a tragedy but the bulletin at least shows that the lessons are being learned and . Europe pmc is a service of the europe pmc funders group in partnership with the european bioinformatics institute jisc the university of manchester and the british library and in cooperation with the national center for biotechnology information at the us national library of medicine ncbi nlm