Insights into a large waterborne Campylobacter outbreak from a cross-sectional telephone survey

To understand the impacts and responses of households during the Havelock North drinking water outbreak.

Fifty days after the outbreak, cross-sectional telephone questionnaires were administered to a cohort of households.

Seventy-six percent of the people surveyed indicated drinking unboiled tap water, with 35% of those developing diarrhoea, compared with only 3% of those who did not drink the water. Symptoms correlated with increasing quantities of water consumed, and 31% reported a relapse of diarrhoea after initial improvement. The attack rate among those less than 20 years old (41%), was higher than those aged 50 and over (22%). Individuals with diarrhoea had an average of 7 days off school or work. Only 27% of individuals with diarrhoea visited a doctor or hospital, but 72% were in households that purchased items from a pharmacy. Following the issue of a boil water notice, 82% of households boiled their water, and 67% purchased bottled water, with only 5% taking no precautions. A third of the 169 households surveyed continued one or both of these responses for at least 3 weeks after the boil water notice was lifted.

Telephone surveys provided insights into the outbreak not otherwise obtainable from routine surveillance systems, including the attack rates among different demographics, size of the outbreak (5,540 cases within Havelock North), potential of pharmacy-based surveillance, compliance with public health messaging and the need to communicate to households when the water is safe to drink.