| Virus properties |
Genomic variation |
Captures the degree of mutation and reassortment as a measure of the genetic diversity of a novel influenza virus; also captures presence or absence of known molecular markers denoting virulence |
| Receptor-binding properties |
Virus-binding preference to glycans with sialic acid in α-2,6 (human) linkage at the terminal galactose when compared with viruses that bind to sialic acid by α-2,3 (avian) linkage |
| Transmissibility in animal models |
Transmission of animal influenza viruses in >1 accepted animal models by direct contact or through respiratory droplets in the absence of direct contact |
| Antiviral treatment susceptibility |
Predicted or demonstrated efficacy of available (approved for human use) antiviral agents against animal influenza viruses |
| Host properties |
Population immunity |
Detection of preexisting cross-reactive serum antibodies acquired through prior infection or vaccination (examined in all age groups) |
| Disease severity |
Spectrum of illness with infection by a novel influenza A virus in humans or in experimentally infected animal models as surrogates for human disease |
| Antigenic relationship to vaccines |
Antigenic relatedness measured by hemagglutination inhibition or virus neutralization tests with postinfection ferret antiserum to emerging virus and seasonal vaccine and reference viruses |
| Ecology and epidemiology |
Human infections |
Occurrence of human infections with animal influenza viruses, frequency of these human infections, and extent of human-to human transmission of these viruses |
| Infections in animals |
The virus’s ability to infect animal species naturally, the number and diversity of those species, ability to maintain sustained natural transmission in those populations, and potential extent of exposure between humans and those animal species |
| Global distribution (in animals) |
Spatial and temporal distribution of animal influenza viruses and the effect of animal production and management systems on the spread among animal populations and potential exposure to humans |
