To test whether these findings could be extrapolated to a currently circulating virus, we next tested the survival of AH04 virus, a 2009 pandemic isolate, on a subset of the materials. Unlike PR8, as a recent clinical isolate this virus does not grow to high titres in the laboratory and nor was a workable plaque assay available. We therefore used a fluorescent focus assay in which live virus is detected by immunofluorescent detection of the viral nucleoprotein in infected cells. To boost the sensitivity with which viable virus could be detected, infectious virus present in the swabs was first amplified by growth in MDCK cells before subsequent assay. The assay therefore provides a highly sensitive but semi quantitative measure of virus infectivity, ideally suited to working with low titre samples [13, 19] . By this measure, the AH04 virus persisted for at least 24 h on the control tissue culture dish material, although titres were evidently lower at 9 and 24 h ( Table 5) . Consistent with the results obtained with PR8 virus, all household surfaces tested showed lower persistence of infectious virus, with none providing recoverable titre at 24 h and the majority failing to produce live material at 9 h. Once again the pine surface showed very rapid inactivation of viability, with no infectivity recovered at 4 h. Thus both an historic virus isolate and an example of the recent pandemic strain fail to survive in high titres for long periods of time on a variety of household surfaces, but with significant survival over shorter time spans on certain materials.