Table 4. Baseline baloxavir susceptibility of seasonal viruses, United States, 2016/17 and 2017/18 influenza seasons.

Virus	Number of virusesa	Baseline EC50 (nM)b
		Range	Mean ± SD	Median
A(H3N2)	28	0.33–1.53	0.83 ± 0.30	0.80
A(H1N1)pdm09	34	0.86–2.86	1.58 ± 0.49	1.57
B Victoria	31	1.79–8.03	4.79 ± 1.48	4.82
B Yamagata	23	1.72–8.29	5.00 ± 1.50	4.92

SD: standard deviation.

^a Seasonal United States influenza viruses collected during May 2017–August 2018 were propagated in cell cultures and used for baseline median EC₅₀ determination.

^b Viruses tested as single titration in a single assay to determine EC₅₀.