Eligibility criteria for cases and controls
| Criteria | Cases | Controls |
| Had diarrhoea (≥3 loose bowel movements in 24 hours) | Include | Exclude |
| Known date of illness onset | Include | NA |
| Household members positive for Campylobacter in 4 weeks prior to onset of illness | Exclude | Exclude (4 weeks prior to interview date) |
| Household members experiencing diarrhoea in 4 weeks prior to onset of illness | Exclude | Exclude (4 weeks prior to interview date) |
| Travelled outside of Australia in 2 weeks prior to onset of illness | Exclude | Exclude (2 weeks prior to interview date) |
| Travelled interstate for the entire 2 weeks prior to onset of illness | Exclude | Exclude (2 weeks prior to interview date) |
| Cannot speak English | Exclude | Exclude |
| Not able to answer questions for some other reason (eg, intellectually disabled) | Exclude | Exclude |
| Not contactable after six telephone attempts | Exclude | Exclude |
| Live outside the catchment areas | Exclude | Exclude |
| Do not have a telephone number available for their primary residence, or a mobile phone | Exclude | Exclude |
| An enteric pathogen other than Campylobacter was isolated/detected in their stool (excluding Blastocystis hominis and Dientamoeba fragilis) | Exclude | NA |
NA, not applicable.