Figure 7. Comparison of Transmission efficiency of pandemic 2009 H1N1 strains during early and later phases of donor infection.

Single donor-single recipient exposures in which the interval between donor instillation and recipient exposure was varied from 1, 3, or 5 donor dpi. Viral culture (hatched bar) is expressed as FFU/mL (total sample) of nasal wash collected on day of exposure (donors) or the greatest value found on day 1−3 post-exposure (recipients). Aerosol data are expressed as genome equivalents/1-hour filter collection; each of three filters was measured in triplicate, and the mean of the three filters reported. For each virus: Cal/04 (green), Cal/07 (blue) and Mex/4482 (red), the donor-recipient pair are aligned horizontally across the figure.