Fig. 4.

Multiple viral gene segments from CA04 confer enhanced transmissibility of KS246 by increasing the release of virus-laden particles into the air. Transmission of (A) Rg-CA04, (B) Rg-KS246, (C) Rg-KS246^{PB2,PB1,PA,NP,NS}×CA04^HA,NA,M, and (D) Rg-CA04^{PB2,PB1,PA,NP,NS}×KS246^HA,NA,M recombinant viruses among ferrets via virus-laden particles that passed through the 5.3-µm impactor. Viral titers (log₁₀TCID₅₀/mL, detection limit at 1.789 log₁₀TCID₅₀/mL) detected in the nasal washes of each recipient ferret. For each recombinant virus, the experiments were independently repeated twice with a total of four recipients. (E) Viral titers detected in the nasal washes of donor ferrets inoculated with 10⁵ TCID₅₀ of the recombinant viruses. Data were plotted for individual donor ferrets (n = 4) and overlaid with mean ± SD. (F) Quantity and size distribution of influenza virus-laden particles sampled from the donor chambers during the exposure period by using the NIOSH bioaerosol sampler. The limit of linear range of quantification (476 M gene copies per cubic meter) is shown. Data were plotted for two independent exposures and overlaid with medians.