Table 1

Attack rate of giardiasis by water supply zone, Bergen municipality Aug-Nov 2004 (n = 795)

Watersupply

Cases

Number of recipents

Attack-rate (per 10,000)

A

637

42,774

148.9

B

15

9,685

15.5

C

89

105,440

8.4

D

33

34,406

9.6

E

4

14,266

2.8

F

13

23,848

5.5

Risk ratio

95% confidence interval

B+C+D+E+F

158

194,519

8.1

Ref.

A

637

42,774

148.9

18.3

15.4 – 21.8

Nygård et al. BMC Public Health 2006 6:141   doi:10.1186/1471-2458-6-141