Hyperendemic Salmonellosis in the Northern Territory of Australia over a 20-Year Period, 2005–2024: An Epidemiological Analysis Using Routine Human Surveillance Data

Nontyphoidal <i>Salmonella</i> bacteria are an important global cause of gastrointestinal disease. In Australia, it is estimated that salmonellosis costs approximately 140 million Australian dollars per year in illness, pain and suffering, and other productivity losses. The Northern Territory (NT) of Australia is a sparsely populated tropical environment, with 31% of the population being Aboriginal Australians. We described the epidemiology of salmonellosis in the NT by analyzing routinely notified salmonellosis cases diagnosed between 2005 and 2024. We performed descriptive, univariate, and multivariate analyses. We used exact logistic regression to explore associations with severe disease (hospitalization or death). We performed negative binomial regression analysis to explore associations with length of hospitalization. There were 9628 salmonellosis notifications equating to a mean annual notification rate of 203 per 100,000 persons-the highest reported in the world; 51% of cases were male; 25.3% had severe disease (2432 hospitalizations and 18 deaths); and 50% were aged <5 years. The most commonly reported serotypes were <i>S</i>. Saintpaul (1125/9628, 11.7%), <i>S</i>. Virchow (1002/9628, 10.4%), and <i>S</i>. Typhimurium (936/9628, 9.7%). Aboriginal people were notified at 1.2 times (95% confidence interval [CI] 1.1-1.2, <i>p</i> < 0.001) the rate of non-Aboriginal people, were 3.7 times (95% CI 3.3-4.1, <i>p</i> < 0.001) more likely to experience severe disease, and were hospitalized for 1.6 times longer (95% CI 1.5-1.8, <i>p</i> < 0.001) than non-Aboriginal people. There was no difference in salmonellosis notification rates in 2005-2014 compared with 2015-2024; however, <i>S</i>. Typhimurium notifications decreased. The tropical climate, abundant wildlife, and contamination of the household environment with <i>Salmonella</i> contribute to high rates of salmonellosis in the NT. Credible interventions are needed to decrease the incidence of salmonellosis, particularly among young children exposed to contaminated tropical environments.