Table 2. Temporal trends of the monthly notification rate (NR) per 100,000 population.

	% Monthly NR growth rate (95% CI)	NR mean level*
		Jan 2006 (95% CI)	Dec 2015 (95% CI)
Total MRSA infections	0.8 (0.7–1.0)	0.51 (0.46–0.56)	1.41 (1.30–1.52)
MRSA infections among cases with an immigrant background	1.3 (1.1–1.5)	0.67 (0.55–0.79)	3.21 (2.90–3.52)
MRSA infections among cases with a Norwegian background	0.6 (0.45–0.72)	0.47 (0.42–0.52)	0.93 (0.85–1.01)
MRSA infections acquired in Norway
All ages	0.4 (0.2–0.5)	0.30 (0.27–0.33)	0.47 (0.42–0.52)
0–19 years	0.7 (0.4–1.0)	0.21 (0.16–0.27)	0.53 (0.43–0.64)
20–39 years	0.4 (0.2–0.7)	0.27 (0.22–0.32)	0.45 (0.38–0.53)
40–69 years	0.3 (0.01–0.5)	0.23 (0.19–0.28)	0.32 (0.27–0.38)
≥70 years	Constant	0.92 (0.84–0.99)	0.92 (0.84–0.99)
MRSA infections acquired abroad
All ages	0.8 (0.6–1.0)	0.14 (0.12–0.16)	0.35 (0.31–0.40)
0–19 years	1.1 (0.7–1.6)	0.10 (0.07–0.15)	0.41 (0.32–0.52)
20–39 years	0.9 (0.6–1.2)	0.18 (0.15–0.22)	0.55 (0.47–0.64)
40–69 years	0.6 (0.3–0.9)	0.13 (0.11–0.16)	0.26 (0.22–0.31)
≥70 years	Constant	0.13 (0.11–0.17)	0.13 (0.11–0.17)
MRSA infections with unknown place of acquisition
All ages	1.6 (1.4–1.8)	0.10 (0.08–0.11)	0.62 (0.56–0.68)
0–19 years	1.7 (1.4–2.1)	0.07 (0.05–0.10)	0.59 (0.50–0.70)
20–39 years	1.8 (1.5–2.1)	0.10 (0.08–0.13)	0.85 (0.74–0.97)
40–69 years	1.6 (1.3–1.9)	0.08 (0.06–0.10)	0.51 (0.43–0.59)
≥70 years	1.0 (0.5–1.4)	0.17 (0.12–0.24)	0.52 (0.40–0.67)

Model-estimated temporal trends of the monthly notification rate per 100.000, by independent quasi-Poisson regressions on separate subsets of the data. The monthly changes, expressed as percentages, and the estimated mean levels of the NRs in January 2006 and December 2015 are reported for each analyzed scenario.

* To compare the NR mean levels, μ, in January 2006 and in December 2015 we used Model 1 (log(μ) = α + β ⋅ t).