Highly pathogenic avian influenza (HPAI). Highly pathogenic avian influenza is defined as follows:
(1) Any influenza virus that kills at least 75 percent of eight 4- to 6-week-old susceptible chickens within 10 days following intravenous inoculation with 0.2 mL of a 1:10 dilution of a bacteria-free, infectious allantoic fluid or inoculation of 10 susceptible 4- to 8-week-old chickens resulting in an intravenous pathogenicity index (IVPI) of greater than 1.2;
(2) Any H5 or H7 virus that does not meet the criteria in paragraph (1) of this definition, but has an amino acid sequence at the haemagglutinin cleavage site that is compatible with highly pathogenic avian influenza viruses; or
(3) Any influenza virus that is not an H5 or H7 subtype and that kills one to five out of eight inoculated chickens and grows in cell culture in the absence of trypsin within 10 days.
9 CFR § 94.0
As used in this part, the following terms shall have the meanings set forth in this section.