Table 1.

Explanatory variables included in the multivariate analysis and their coding

Explanatory variables	Coding
Symptoms from IID2 questionnairea
Diarrhoea days	>3 days = 1 ⩽3 days = 0
Bloody diarrhoea	Yes = 1 No = 0
Vomiting days	>3 days = 1 ⩽3 days = 0
Nausea	Yes = 1 No = 0
Nausea days	>3 days = 1 ⩽3 days = 0
Abdominal pain	Yes = 1 No = 0
Loss of appetite	Yes = 1 No = 0
Fever	Yes = 1 No = 0
Headache	Yes = 1 No = 0
Cough/nose/throat	Yes = 1 No = 0
Combined symptom variables
Diarrhoea but no vomiting	Yes = 1 No = 0
Vomiting but no diarrhoea	Yes = 1 No = 0
Participant characteristics
Ageb	>16 years = 0, 5–16 years = 1, <5 years = 2
Date of onsetb	Autumn(0), Winter(1), Spring(2), Summer(3)c

^a‘Not sure’ responses from the original questionnaires were left blank and treated as missing data.

^bCoded as factors for analysis.

^cSeasons defined by meteorological calendar.