. 2022 Mar;28(3):639–649. doi: 10.3201/eid2803.211752

Table 5. Survival times and half-lives of various recombinant viruses on a plastic surface*.

Subtype†	Median survival time (95% CI), h‡	Median half-life (95% CI), h§
Subtype†	Median survival time (95% CI), h‡	4 (log₁₀ FFU)	3 (log₁₀ FFU)	2 (log₁₀ FFU)
rH5N1-H5N3-NA	8.15 (6.86–9.62)	0.41 (0.34–0.51)	0.55 (0.45–0.68)	0.82 (0.67–1.02)
rH5N1-H5N3-HA	8.17 (6.88–9.63)	0.41 (0.34–0.51)	0.55 (0.45–0.68)	0.83 (0.68–1.02)
rH5N3-H5N1-NA	23.68 (21.26–26.25)	1.14 (1.02–1.28)	1.52 (1.36–1.71)	2.28 (2.04–2.57)
rH5N3-H5N1-NS	7.74 (6.59–9.03)	0.39 (0.33–0.48)	0.53 (0.44–0.64)	0.79 (0.65–0.96)
rH5N3-H5N1-M	8.75 (7.52–10.11)	0.45 (0.38–0.54)	0.60 (0.50–0.72)	0.90 (0.75–1.08)
rH5N3-H5N1-HA	7.69 (6.59–8.93)	0.39 (0.33–0.47)	0.52 (0.44–0.63)	0.78 (0.65–0.95)

*FFU, focus-forming unit. †A/crow/Kyoto/53/04 (H5N1) recombined with the NA and HA genes of A/Duck/Hong Kong/820/80 (H5N3) are defined as rH5N1-H5N3-NA and rH5N1-H5N3-HA. In addition, A/Duck/Hong Kong/820/80 (H5N3) recombined into the NA, NS, M, and HA genes of A/crow/Kyoto/53/04 (H5N1) was defined as rH5N3-H5N1-NA, rH5N3-H5N1-NS, rH5N3-H5N1-M, rH5N3-H5N1-HA. ‡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 3). 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 time. §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.