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Volume 9, Number 1—January 2003

Research

Two Epidemiologic Patterns of Norovirus Outbreaks: Surveillance in England and Wales, 1992–2000

Ben Lopman*Comments to Author , Goutam K Adak*, Mark Reacher*, and David W.G. Brown*
Author affiliations: *Public Health Laboratory Service, London, United Kingdom

Main Article

Table 3

Outbreak characteristics compared by setting of outbreak, England and Wales, 1992–2000

Setting Median
(days) N Geometric mean of duration (days)(95% CI)a t test p value
Duration of outbreaks





Hospital
8
679
8.8 (8.4 to 9.3)


Residential facilities
9
664
8.7 (8.1 to 9.4)
–0.321
0.73
School
8
63
8.1 (6.8 to 9.7)
–0.879
0.40
Food outlet
3
94
3.3 (2.8 to 3.8)
–12.699
<0.0001
Hotel
5
133
4.3 (3.6 to 5.1)
–7.025
<0.0001
Other
4
69
4.3 (3.6 to 5.1)
–8.043
<0.0001
All settings
8
1,702
7.7 (7.5 to 8.0)


Numbers affected per outbreak





Hospital
17
751
17.5 (16.4 to 18.5)


Residential facilities
23
723
21.5 (19.8 to 23.3)
4.895
<0.0001
School
24
73
24.9 (20.5 to 30.3)
3.594
<0.0001
Food outlet
23
104
23.4 (19.8 to 27.6)
3.444
0.001
Hotel
29
147
26.5 (23.0 to 30.6)
5.729
<0.0001
Other
29
74
24.5 (20.2 to 29.7)
3.432
0.001
All settings 21 1,872 20.3 (19.7 to 21.1)

aCI, confidence interval.

Main Article

Appendix: Surveillance and analysis definitions

Outbreak: an incident in which two or more people, thought to have a common exposure, experience a similar illness or proven infection, at least one of them being ill (22).
General outbreak: an outbreak that affects members of more than one household, or residents of an institution (36).
General outbreak of Norovirus: a general outbreak in which Norovirus is determined to be the causative agent by electron microscopy, RT-PCR, or enzyme immunoassay in one or more affected persons.
Residential facilities: includes residential homes, which provide some assistance in day-to-day living, and nursing homes, which provide care for persons whose infirmity or illness requires nursing care on a regular basis.
Food outlets: commercial food retailers including restaurants, pubs, bars, cafeterias, mobile food vendors, and caterers.

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