FIG 4.

Proportions of BXA-Sen and BXA-Res virus subpopulations in the URTs of ferrets inoculated with the BR/08-I38T virus. All virus-positive ferret nasal washes were processed for amplification of the full-length PA gene by RT-PCR. The proportions of the respective PA I38 and I38T subpopulations were determined by using the Illumina sequencing platform to call variants in the nucleotides encoding the amino acid at position 38 of the PA protein. High-quality reads were mapped to the consensus PA sequence of the BR/08 virus. The data shown are the virus proportions (expressed as the percentages of the total reads) in individual ferrets.