Direct contact virus transmission experiments in chickens were conducted per the procedure of (Yuan et al., 2014). Briefly, the chickens of inoculated groups (n = 6) were intranasally inoculated with 0.2 mL of 105 EID50 of either the SW8 or ZH283 virus in a ABSL-3 laboratory, and after 24 h, additional naïve contact groups (n = 3) were also intranasally inoculated with 0.2 mL of PBS and placed in physical contact in the same cage to share feed and water with chickens inoculated with the virus. At 3 days post-infection (DPI), three inoculated chickens were humanely euthanized, and target tissues (i.e., brain, lung, spleen, and bursa of Fabricius) were harvested to determine viral titers and for RNA extraction. At 3, 5, 7, 9, and 11 DPI, oropharynx and cloacal swabs samples were collected for the detection of viral shedding and suspended in 1 mL of PBS. All tested tissues and swabs samples were harvested for viral detection and titration in SPF chick embryos. All surviving chickens were euthanized at 14 DPI, and the serum was harvested and tested for seroconversion by hemagglutination inhibition testing using 1% turkey erythrocytes (Stephenson et al., 2004).