Underlying medical conditions, body mass index and illness characteristics of index cases, according to age group.

IQR = interquartile range.*p**p***p1Body Mass Index (BMI, weight in kilograms divided by height squared in metres) Excludes one pregnant women, one child under two, and 8 patients (6 children and 2 adults) missing height or weight data.2Excludes one child and 6 adults with missing data.3Excludes eight adults with missing data.