Extended Data Fig. 7: The advantage of the N501Y substitution and Alpha-spike/WT-non-spike variant during the transmission from donor to recipient hamsters.

a–d, The ratios of mixed viruses in the nasal washes (a, c), tracheae and lungs (b, d) of recipient hamsters were compared to the ratios of N501Y:wt or Alpha-spike/WT-non-spike:wt measured on the day 1 nasal wash of donor hamsters to assess fitness for transmission to and early replication in the recipient hamsters, respectively. The total infection titer of the mixed viruses was 10⁵ PFU per hamster. Red dots represent individual animals (n = 5; n = 10 in day 1 nasal wash of N501Y group), the horizontal lines in each catseye represent the mean, shaded regions represent standard error of the mean; y-axes use a log₁₀ scale. Black numbers above each set of values (catseye) indicate the relative fitness estimates. P values are calculated for the group (strain) coefficient for each linear regression model.