Volume 9, Number 1—January 2003
Research
Two Epidemiologic Patterns of Norovirus Outbreaks: Surveillance in England and Wales, 1992–2000
, Goutam K Adak*, Mark Reacher*, and David W.G. Brown*
Table 2
Microbiologic and statistical evidence of foods implicated in outbreaks of Norovirus, England and Wales
| Implicated food | Microbiologic evidence | Cohort study | Case-control study | Any evidence | Total no. of outbreaks in which food vehicle implicated |
|---|---|---|---|---|---|
| Oysters |
5 (25%)a |
9 (45%) |
0 |
14(70%) |
20 |
| Poultry |
0 |
6 (67%) |
0 |
6 (67%) |
9 |
| Meat |
0 |
3 (60%) |
0 |
3 (60%) |
5 |
| Fish |
0 |
3 (50%) |
1 (16%) |
4 (67%) |
6 |
| Salads and vegetables |
0 |
10 (59%) |
3 (18%) |
13 (76%) |
17 |
| Other items |
0 |
16 (55%) |
3 (10%) |
19 (65%) |
29 |
| Total | 5 (6%) | 47 (55%) | 7 (8%) | 59 (68%) | 86 |
aPercentages represent outbreaks with evidence per total outbreaks where food vehicle was implicated.
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.