Timing of contact and airborne transmission.

(A) Transmission time based on the mode of transmission and virus inoculum in donor mice. The day of transmission was recorded based on the day of experiment. Day 0 is the day donor mice were directly inoculated intranasally with either 70- or 7,000-PFU of rSeV-luc(M-F*). For contact transmission, naïve recipient mice were caged with donor mice 1 day after direct inoculation. For airborne transmission, naïve recipient mice were caged with infected donor mice directly after inoculation. Reported is the first day when bioluminescence signal exceeded the limit of detection (5.5 log10 photons/sec) in any respiratory tissue. (B) Time of airborne transmission based on whether the dynamics of primary infection were tracheal dominant or respiratory tract disseminated. Significance was determined by Student's t-test: *** p = 0.0003 and ** p = 0.001. n.t. on the y-axis of panel A = no transmission.