Table 2. Survival times and half-lives of various subtypes of influenza viruses on the surface of human skin*.

Subtype	Median survival time (95% CI), h†	Median half-life (95% CI), h‡
		4 (log10 FFU)	3 (log10 FFU)	2 (log10 FFU)
H5N1-Ky	4.66 (4.21–5.13)	0.20 (0.18–0.23)	0.27 (0.24–0.30)	0.40 (0.36–0.45)
H5N1-Eg	4.54 (4.14–4.97)	0.20 (0.18–0.22)	0.26 (0.24–0.29)	0.40 (0.36–0.44)
H7N9	1.96 (1.84–2.08)	0.08 (0.08–0.09)	0.11 (0.11–0.12)	0.17 (0.16–0.18)
H5N3	2.10 (1.94–2.26)	0.09 (0.08–0.10)	0.12 (0.11–0.13)	0.18 (0.17–0.20)
H5N9	2.03 (1.89–2.17)	0.09 (0.08–0.09)	0.12 (0.11–0.13)	0.18 (0.16–0.19)
H3N2	2.03 (1.89–2.17)	0.09 (0.08–0.10)	0.12 (0.11–0.13)	0.18 (0.16–0.19)
H1N1-PR8	1.97 (1.83–2.12)	0.08 (0.08–0.09)	0.11 (0.10–0.12)	0.17 (0.15–0.18)
H1N1-Ok-pdm	2.10 (1.93–2.27)	0.09 (0.08–0.10)	0.12 (0.11–0.13)	0.18 (0.17–0.20)

*FFU, focus-forming unit; H5N1-Ky, A/crow/Kyoto/53/04 (H5N1); H5N1-Eg, A/chicken/Egypt/CL6/07 (H5N1); H7N9, A/Anhui/1/23 (H7N9); H5N3, A/Duck/Hong Kong/820/80 (H5N3); H5N9, A/Turkey/Ontario/7732/66 (H5N9); H3N2, Clinical strain (H3N2); H1N1-PR8, A/Puerto Rico /8/1934 (H1N1); H1N1-Ok-pdm, A/Osaka/64/2009 (H1N1). †The elapsed time was used as the explanatory variable (x-axis), and the logarithmic virus titer was used as the explained variable (y-axis). A linear regression analysis with logarithmic link function was performed for each virus to create a curve of regression (Appendix Figure 2). Because the detection limit of each influenza virus titer was 10¹ FFUs, the X value (when the Y value of the regression curve was 1.0) was used as the survival times. ‡The half-life of each virus was calculated from the slope of each regression curve when the amount of virus remaining on the surface was 2, 3, or 4 log₁₀ FFUs.