Evaluation of three strains of influenza A virus in humans and in owl, cebus, and squirrel monkeys

Abstract

Virulence of 3 cloned influenza A viruses was compared in humans and in 3 readily available species of non-human primates (owl, squirrel and cebus monkeys) to identify a monkey species that could be used to investigate the genetic basis of attenuation of influenza A viruses for humans. Three influenza A viruses from 2 subtypes, i.e., the A/Udorn/72 (H3N2), A/Alaska/77 (H3N2) and A/Hong Kong/77 (H1N1) viruses, produced febrile influenzal illness in humans. Squirrel monkeys developed mild uper respiratory tract illness in response to each of the 3 viruses. Illness was accompanied by a high level of virus shedding; each of 9 squirrel monkeys that shed equal to or greater than 105.0 tissue culture infective doses of virus became ill, whereas those that shed less remained well. The cebus and owl monkeys remained clinically well despite infection with each of the 3 viruses. Squirrel monkeys may be moderately permissive primate hosts in which to investigate the genetic basis of virulence of human influenza A viruses.