After eradication of circulating polioviruses, reintroduction might arise from cultured laboratory stocks, or from collections of patients' or environmental samples. In an example of a further class of risk, we recorded poliovirus type 1 in at least four working stocks of what had been identified as various serotypes of human rhinovirus. This finding emphasises the need to urgently assess the possibility of presence of poliovirus, even in apparently well-characterised stocks of other viruses, to screen for the virus where necessary, and to destroy materials in which risk outweighs potential benefit.
Bibliographical noteFunding Information:
We thank David Tyrrell, former Director of the Medical Research Council Common Cold Research Unit, who provided helpful background information. We acknowledge financial support from the Wellcome Trust (grants 056726 and 068686) and the Office of Science and Technology for the NCPV. The funding sources had no role in study design, data collection, data analysis, data interpretation, or writing of the report.