The changing epidemiology of shigellosis in Australia, 2001-2019

Shigellosis is an increasing cause of gastroenteritis in Australia, including prolonged outbreaks in remote Aboriginal and Torres Strait Islander (hereafter “First Nations”) communities and among men who have sex with men (MSM) in major cities. To determine associations between Shigella species and demographic and geographic factors we used negative binomial regression to analyse national case notifications of shigellosis from 2001 to 2019. S. sonnei and S. flexneri accounted for 42% and 29% of cases, respectively. Nationally, notification rates increased from 2001 to 2019 with yearly incidence rate ratios of 1.04 (95% CI 1.02-1.07) for S. boydii , 1.05 (95% CI 1.04-1.06) for S. sonnei and 1.04 (95% CI 1.04-1.06) for S. flexneri . Children aged 0-4 years had the highest burden of infection for S. flexneri, S. sonnei and S. boydii ; and males had a higher notification rate for S. sonnei (incidence rate ratio 1.24, 95% CI 1.15-1.33), reflecting transmission among MSM. First Nations Australians were disproportionately affected by shigellosis, with the notification rate in this population peaking in 2018 at 92.1 cases per 100,000. The findings of this study provide important insights into the epidemiological characteristics of shigellosis in Australia, and can be used to inform targeted public health prevention and control strategies.