Survival of White Leghorn chickens and transmission of virus to naive contact birds following intranasal inoculation with P0 rH5N3 versus P6 rH5N3. (A) Ten chickens, each in separate isolation cubicles, were intranasally inoculated with 40,000 PFU of either P0 rH5N3 or P6 rH5N3, and survival was monitored over a period of 20 days. (B and D) Oropharyngeal and cloacal swabs from P0 rH5N3- and P6 rH5N3-inoculated birds (B) or from P0 rH5N3 and P6 rH5N3 contact birds (D) were tested by qRT-PCR to assess virus shedding. (C) One day following inoculation, five naive contact birds were placed in each isolation cubicle and allowed to commingle with the infected birds. The survival of the contact birds was monitored for a period of 19 days.