Table 1.

Contribution of receptor binding to 1918 virus transmission in ferrets.

Virusa	Description	190b	225b	α2-6c	α2-3c	Transmissiond
Tx/91	Seasonal H1N1 virus	D	D	Yes	No	3/3
SC/18	Reconstructed 1918 virus	D	D	Yes	No	3/3
NY/18	Natural variant 1918 virus	D	G	Yes	Yes	2/3e
AV/18	“avianized” 1918 virusf	E	G	No	Yes	0/3
Dk/NY	Avian H1N1	E	G	No	Yes	0/3
Dk/NY-DD	Avian H1N1 with HA mut	D	D	Yes	No	0/3

^aTx/91, A/Texas/36/1991; SC/18, A/South Carolina/1/1918; NY/18, A/New York/1/1918; AV/18, NY/18 virus with D190E mutation in HA; Dk/NY, A/duck/New York/15024-21/1996; Dk/NY-DD, Dk/NY virus with E190D and G225D mutation in HA.

^bAmino acid position (H3 numbering). D, aspartic acid; G, glycine; E, glutamic acid.

^cPresence or absence of hemagglutination using resialylated red blood cells. Data previously published in (Glaser et al., 2005; Tumpey et al., 2007; Van Hoeven et al., 2009b).

^dRespiratory droplet transmissibility of reassortant viruses in the ferret model (number of contact ferrets with detectable virus in nasal wash specimens and seroconversion to homologous virus/total number of contact ferrets unless specified otherwise).

^eOne ferret represented in numerator seroconverted to homologous virus in the absence of virus detection.

^f“avianized”, variant SC/18 virus with two amino acid changes in the HA to change receptor binding specificity from a2-6 to a2-3.