Table 2.

Properties of parental and 7:1 chimeric viruses used in this study

^aThrste origin of each of the eight gene segments is shown by shading (originated from the 1918 virus) or lack of shading (originated from the AI virus). For the first virus, the 1918 pandemic influenza virus, all eight of the gene segments were from the 1918 virus and are shaded. For the second virus listed, the 1918^AI-PB2 virus, the PB2 gene segment was from the AI virus (not shaded) and the remaining seven gene segments were from the 1918 virus (shaded).

^bData presented as log₁₀ PFU.

^cBD, below the limit of detection. ND, not done.