Describing the Epidemiology of Gastroenteritis Outbreaks in the Northern Territory of Australia, 2005–2024

Abstract

In Australia, circa 2019, there were an estimated 4.7 million cases of foodborne illness, resulting in costs of approximately 3 billion Australian dollars (AUD) per year. The Northern Territory (NT) is Australia’s most sparsely populated jurisdiction and has the highest proportion of Aboriginal Australians. We analyzed data on gastroenteritis outbreaks that occurred in the NT between 2005 and 2024 to describe the transmission routes, pathogens, trends and estimate costs in AUD of foodborne outbreaks. There were 408 outbreak investigations conducted between 2005 and 2024, a median of 20.5 investigations per year (range 6–35). While the annual incidence of foodborne and nonfoodborne outbreaks did not vary significantly over time, the incidence of salmonellosis outbreaks fell to 2.1 per year between 2015 and 2024 compared with 5.2 per year between 2005 and 2014 (p < 0.005). Salmonella was the most commonly identified etiological agent (73/408 outbreaks, 17.9%) followed by norovirus (45/408, 11.0%), Shigella (20/408, 4.9%), Cryptosporidium (17/408, 4.2%), and rotavirus (15/408, 3.7%). The most common outbreak transmission mode was probable person to person (146/408 outbreaks, 36%), followed by foodborne (102/408, 25%). Childcare centers were the most common settings (112/408, 27%), followed by those that occurred in the community (87/408, 21%), private residences (44/408, 10.8%), restaurants/cafes (37/408, 9.1%), and camps (23/408, 5.6%). The most common cause of foodborne outbreaks was food handler contamination (16/102, 15.6%%), followed by ingestion of contaminated raw products (15/102, 14.7%) and cross-contamination of food from raw ingredients (7/102, 6.8%). We estimated that the cost of foodborne disease outbreaks in the NT over the 20-year period was AUD 859,868 (90% uncertainty interval [UI] AUD 782,142–AUD 940,774] with a median of AUD 34,900 per year. Foodborne salmonellosis outbreaks accounted for AUD 494,360 (90% UI AUD 456,470–AUD 540,280), approximately 57% of the total cost of foodborne outbreaks.