TABLE 1 .

Strains deep sequenced in this study^a

Sample	Strain	Passage history	Site 151 genotype	Ct value
WSPHL1	A/Washington/10/2013	C1/C1	X	23.19
WSPHL2	A/Washington/13/2013	C1	X	17
WSPHL3	A/Washington/17/2013	C2	X	24.57
WSPHL4	A/Washington/18/2013	C3	X	21.52
WSPHL5	A/Washington/08/2014	C1	X	22.8
WSPHL6	A/Washington/07/2015	S3	X	23.78
WSPHL7	A/Washington/24/2015	S3	X	17.4
WSPHL8	A/Washington/32/2015	S3	X	18.69
WSPHL9	A/Washington/36/2015	S3	X	25.03

^aGenotypes were determined by Sanger sequencing of passaged isolates and are taken from those reported in the GISAID EpiFlu database. Annotations of passage history are not standardized, but Cn generally refers to n passages of the virus in cell culture prior to sequencing and Sn generally refers to n passages of the virus in MDCK-SIAT1 cells (17). For the genotype at site 151, an annotation of X indicates a mixture of D151 and G151 in the original Sanger sequencing. The C_t value is the amount of viral material in the original clinical sample as determined by quantitative PCR.