Figure 1Phylogenetic analysis of the norovirus detected from patients, food handlers, and environmental samples (unheated foods, supplemental water, and groundwater). The phylogenetic tree was constructed with the neighbor-joining method with norovirus partial capsid region (312-314bp). The numbers in the branches indicate the bootstrap values.
Table 1Comparison of epidemiological and laboratory characteristics.
Features of outbreaks |
Outbreak A |
Outbreak B |
Outbreak C |
Epidemiological features |
Attack rate (%) |
326/2007 (16.24) |
27/656 (4.1) |
36/214 (16.8) |
Symptomatic patients |
326 |
27 |
36 |
Date of onset |
Nov 21, 2012 |
Nov 30, 2012 |
Nov 30, 2012 |
Scale(s) |
Large |
Medium |
Medium |
Type of setting |
School |
School |
School |
Clinical symptoms (%) |
Diarrhea |
326/326 (100) |
23/27 (85.2) |
26/36 (72.2) |
Nausea |
223/326 (68.4) |
24/27 (88.9) |
24/36 (66.7) |
Abdominal pain |
205/326 (62.9) |
25/27 (92.6) |
17/36 (47.2) |
Vomiting |
156/326 (47.9) |
14/27 (51.9) |
26/36 (72.2) |
Fever |
190/326 (58.3) |
14/27 (51.9) |
17/36 (47.2) |
Laboratory test |
No. of examinations of patients |
99 |
10 |
22 |
Positive samples |
46 |
2 |
12 |
Genogroup I |
— |
— |
— |
Genogroup II |
46 |
2 |
12 |
No. of examinations of food-handlers |
28 |
14 |
5 |
Positive samples |
2 |
5 |
2 |
Genogroup I |
— |
— |
— |
Genogroup II |
2 |
5 |
2 |
Environmental samples |
13 |
Causative foods (unheated foods) |
9 |
Genogroup I |
— |
Genogroup II |
9 |
Supplemental water |
3 |
Genogroup I |
— |
Genogroup II |
3 |
Groundwater |
1 |
Genogroup I |
— |
Genogroup II |
1 |
Table 2Oligo nucleotide sequences of primers used in this study.
Genogroup |
Name of primer |
Sequence (5′→3′) |
Application |
GI |
NoGI-F1 |
ATGGCCATGTTCCGITGGATG |
Stool specimen |
NoGI-F2 |
CGGGCCCGAATTYGTAAATGATG |
NoGI-R |
CCAACCCARCCATTRTACATYTG |
GI-F1M |
CTGCCCGAATTYGTAAATGATGAT |
Stool & environmental samples |
GI-F2 |
ATGATGATGGCGTCTAAGGACGC |
NoGI-R |
CCAACCCARCCATTRTACATYTG |
GII |
NoGII-F1 |
CCCTCGAGGGCGATCGCAATCT |
Stool specimen |
NoGII-F2 |
CACAATTGTGAATGAAGATGGCGTCGA |
NoGII-R |
CCRCCIGCATRICCRTTRTACAT |
GII-F1M |
GGGAGGGCGATCGCAATCT |
Stool & environmental samples |
GII-F3M |
TTGTGAATGAAGATGGCGTCGART |
NoGII-R |
CCRCCIGCATRICCRTTRTACAT |
Table 3Distribution of norovirus GII-4 variant analyzed in this study.
Name of variant |
Outbreak A |
Outbreak B |
Outbreak C |
Environmental samples |
2006b |
— |
— |
1 (7.1) |
— |
2010 |
— |
— |
— |
2 (16.7) |
2012 |
44 (100) |
7 (100) |
13 (92.9) |
10 (83.3) |