Experimental setup of the co-infection study. Broiler groups: Non infected group (control negative). Bacteria inoculated group (E. coli alone). Virus inoculated group (vNDV alone). Simultaneous inoculation of virus and bacteria (vNDV+E. coli). Bacteria inoculation followed by virus inoculation (E. coli/vNDV). Virus inoculation followed by bacteria inoculation (vNDV/E. coli). *Necropsy days.