Fig. 2. A/H1N1, A/H3N2 and A/H5N1_AT viruses were transmitted from the upper respiratory tract of ferrets.

Ferrets were inoculated with 10⁵ TCID₅₀ of untagged (shown in red) and tagged (shown in blue) virus pairs of A/H1N1 virus (a Donors 5–8), A/H3N2 virus (b Donors 9–12) or A/H5N1_AT virus (c Donors 13–16). Untagged and tagged viruses were inoculated either intranasally or intratracheally as indicated by the color coding in the schematic ferret representations. Untagged and tagged virus proportions at the day of virus transmission are represented by the pie charts for both donor and recipient ferrets. URT: upper respiratory tract, i.e., nasal turbinates, LRT: lower respiratory tract, i.e., combined data from two parts of the trachea and the lungs, N: nose swabs, T: throat swabs. X means that no transmission was observed. Transmission was defined by the detection of two consecutive swabs with a RT-qPCR threshold (CT-value) of 35. Source data are provided as a Source Data file.