Surfaces were cut into 2 cm 2 pieces and sterilised by a variety of means depending on the surface to be tested (e.g. autoclaving, fumigation etc). Sterile surfaces were glued into sterile 6-well tissue culture dishes using cyanoacrylate adhesive (Henkel, UK). Preliminary experiments (data not shown) demonstrated that dried adhesive alone was non-inhibitory to influenza virus. Under the same conditions of temperature and humidity (ranges 17-21uC and 23-24% respectively), 10 ml volumes of virus were applied to six samples of each surface at the same time. Sampling was conducted immediately -time zero -to demonstrate recoverability. A cotton swab was moistened by dipping in 3 ml of virus transport medium (VTM, Remel, UK) and then wiped carefully in 6 different directions for 1 minute across the top of the surface. Keeping everything on ice, the swab was placed into the tube containing the residual (3 ml) volume of VTM and vortexed for 1 minute. After this, the sample was split directly into 6 eppendorf tubes and stored on dry ice prior to freezing at 270uC. The remaining samples in the plate were kept in a plastic, lidded box at constant temperature and humidity. At 4, 9, 24, 48 and 72 hrs, further samples were taken and stored. After initial experiments it was clear that the virus did not survive in detectable amounts for more than 24 hrs, therefore for the majority of the experiments only the first 4 time points (0, 4, 9, and 24 hrs) were taken. Initial experiments with PR8 virus also showed that loss of virus on the swab was not a major factor, with recovery of virus at time zero from polypropylene surfaces approaching 50% of initial titre (data not shown).