From: An outbreak of acute norovirus gastroenteritis in a boarding school in Shanghai: a retrospective cohort study
Grade
Number
Cases
Attack rate (%)
1
182
28
15.38
2
175
30
17.14
3
166
16.87
4
158
44
27.85
5
150
53
35.33
6
173
8
4.62
7
171
22
12.87
132
15
11.36
9
118
10
8.47
94
11
11.70
95
5.26
12
79
0
0.00
Total
1693
254
15.00