The following criteria have been adopted by the OIE for determining pathogenicity of an
influenza A virus:
a) One of the two following methods to determine pathogenicity in chickens is used. A high
pathogenicity influenza A virus is:
i) any influenza A virus that is lethal3 for six, seven or eight of eight 4- to 8-week-old
susceptible chickens within 10 days following intravenous inoculation with 0.2 ml of a
1/10 dilution of a bacteria-free, infective allantoic fluid
or