Disclosed is a method of selecting a human influenza virus for growth on tissue culture cells by limiting dilution cloning, the method comprising: a) serially diluting a quantity of human influenza virus to obtain a series of dilutions with decreasing concentrations of human influenza virus b) contacting the human influenza virus of each of the series of dilutions with tissue cultured cells c) growing the human influenza virus that were contacted in step b for a time sufficient to produce cytopathic effects (CPE) d) harvesting a human influenza virus grown in step c from tissue cultured cells that were contacted with human influenza virus from the highest dilution within the series of dilutions that causes CPE and e) repeating steps a through d with a quantity of human influenza virus harvested in step d. Also disclosed is the use of the method in selecting canine influenza.
