Volume 20, Number 7—July 2014
Research
Norovirus Epidemiology in Community and Health Care Settings and Association with Patient Age, Denmark
, Jannik Fonager, Annette K. Ersbøll, and Blenda Böttiger
Table 2
Association between age and infection with norovirus GII.4, Denmark, 2006–2010*
| Variable | All patients with an assigned genotype, n = 1,952 |
Sensitivity analysis 1, n = 1,299 patients |
Sensitivity analysis 2, n = 1,566 patients |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Total no. (%)† | No. (%) positive for GII.4‡ | OR | 95% CI | OR | 95% CI | OR | 95% CI | |||
| Community settings | ||||||||||
| Age, y | ||||||||||
| <3 | 558 (63) | 291 (52) | 0.60 | 0.39–0.91 | 0.46 | 0.25–0.86 | 0.63 | 0.40–1.00 | ||
| 3–19 | 80 (9) | 21 (26) | 0.19 | 0.10–0.37 | 0.09 | 0.03–0.24 | 0.22 | 0.11–0.43 | ||
| 20–39 | 114 (13) | 73 (64) | Ref | NA | Ref | NA | Ref | NA | ||
| 40–59 | 66 (7) | 43 (65) | 1.03 | 0.54–1.95 | 0.86 | 0.30–2.42 | 1.07 | 0.55–2.08 | ||
| ≥60 | 64 (7) | 53 (83) | 2.71 | 1.27–5.78 | 2.23 | 0.73–6.88 | 2.86 | 1.32–6.19 | ||
| Health care settings |
||||||||||
| Age, y | ||||||||||
| <3 | 25 (2) | 13 (52) | 0.46 | 0.16–1.29 | 0.50 | 0.13–1.98 | 0.75 | 0.25–2.22 | ||
| 3–19 | 12 (1) | 6 (50) | 0.41 | 0.11–1.52 | 0.23 | 0.04–1.19 | 0.58 | 0.14–2.41 | ||
| 20–39 | 44 (4) | 31 (71) | 1 (Ref) | NA | 1 (Ref) | NA | 1 (Ref) | NA | ||
| 40–59 | 119 (11) | 107 (90) | 3.73 | 1.54–9.05 | 3.42 | 1.20–9.72 | 4.59 | 1.75–12.09 | ||
| ≥60 | 870 (81) | 828 (95) | 8.39 | 4.07–17.29 | 8.37 | 3.55–19.78 | 9.62 | 4.38–21.12 | ||
| Sex | ||||||||||
| M | 965 (49) | 716 (74) | 1.23 | 0.96–1.56 | 1.26 | 0.92–1.74 | 1.22 | 0.95–1.58 | ||
| F | 987 (51) | 750 (76) | Ref |
NA |
Ref |
NA |
Ref |
NA |
||
| Estimate |
SE |
Estimate |
SE |
Estimate |
SE |
|||||
| Variation between clusters§ | NA | NA | 0.053 | 0.089 | 0.062 | 0.101 | NA | NA | ||
| Intraclass correlation coefficient | NA | NA | 2.6% | NA | 1.95% | NA | NA | NA | ||
| Dispersion parameter | NA | NA | 0.99 | NA | 0.99 | NA | 1.01 | NA | ||
*Sensitivity analysis 1 was a multilevel logistic regression model that included only wards and clinics with ≥5 patients. Sensitivity analysis 2 was a logistic regression model (without random effect) that included only the first patient per month within each ward and clinic. GII, genogroup II; OR, odds ratio; Ref, referent; NA, not applicable. An OR>1 indicates an increased risk for norovirus GII.4 infection compared with patients 20–39 y of age.
†Proportions for community settings do not add up to 100% because of rounding.
‡Proportion of patients infected with norovirus GII.P4 or GII.4 in each age or sex group.
§Estimated to be 1.12 (SE 0.18) in the random intercept-only model (i.e., without the effect of age, sex, and setting).