Clinical symptoms and death of chickens infected by intravenous injection (A) and intranasal/tracheal inoculation (B) with H7N3 virus isolation 1, at several hours after infection. Sixteen chickens were inoculated, of which 4 were euthanized at 24 h postinfection for further analysis. Clinical conditions are indicated according to the color legend as follows: normal, without symptoms; sick, mild clinical symptoms; very sick, severe clinical symptoms.