The campylobacteriosis conundrum - Examining the incidence of infection with Campylobacter sp. in Australia, 1998-2013

Campylobacter sp. are a globally significant cause of gastroenteritis. Although rates of infection in Australia are among the highest in the industrialized world, studies describing campylobacteriosis incidence in Australia are lacking. Using national disease notification data between 1998 and 2013 we examined Campylobacter infections by gender, age group, season and state and territory. Negative binomial regression was used to estimate incidence rate ratios (IRRs), including trends by age group over time, with post-estimation commands used to obtain adjusted incidence rates. The incidence rate for males was significantly higher than for females [IRR 1.20, 95% confidence interval (CI) 1.18-1.21], while a distinct seasonality was demonstrated with higher rates in both spring (IRR 1.18, 95% CI 1.16-1.20) and summer (IRR 1.17, 95% CI 1.16-1.19). Examination of trends in age-specific incidence over time showed declines in incidence in those aged <40 years combined with contemporaneous increases in older age groups, notably those aged 70-79 years (IRR 1998-2013: 1.75, 95% CI 1.63-1.88). While crude rates continue to be highest in children, our findings suggest the age structure for campylobacteriosis in Australia is changing, carrying significant public health implications for older Australians.