Among the avian influenza A virus subtypes, the H5N1 and H9N2 viruses have the potential to cause an influenza pandemic because they are widely prevalent in avian species in Asia and have demonstrated the ability to infect humans. We sought to determine if rapid assays routinely used in clinical microbiology laboratories, the shell vial assay using A549 and RhMK cells and two commercial antigen capture enzyme immunoassays (EIA), could detect wild type (wt) and cold adapted (ca) avian influenza A H5N1 and H9N2 viruses. At concentrations of 20 and 20,000 TCID50 H5N1 ca virus was detected after 1, 2, and 5 days of incubation equally well in both A549 and RhMK cells. The H5N1 wt virus at 2 x 104 TCID50 was also detected in both cell lines, but at 20 TCID50 the wt virus was only detected at 5 days in A549 cells and at 2 and 5 days in RhMK cells. The H9N2 wt virus was detected at both concentrations after 1,2, and 5 days of incubation equally well in both cell lines. The H9N ca virus was also detected in both cell lines at 20,000 TCID50, but at 20 TCID50 the ca virus was only detected at 5 days in A549 cells and at 2 and 5 days in RhMK cells. We found for the commercial EIAs H9N2 wt and ca viruses were detected by both assays at 50,000 TCID50. The H5N1 ca virus was detected at 50,000 TCID50 in both assays, but the wt virus was not detected in either assay at this concentration.
