Vibrio parahaemolyticus Foodborne Illness Associated with Oysters, Australia, 2021-2022

Abstract

The bacterium Vibrio parahaemolyticus is ubiquitous in tropical and temperate waters throughout the world and causes infections in humans resulting from water exposure and from ingestion of contaminated raw or undercooked seafood, such as oysters. We describe a nationwide outbreak of enteric infections caused by Vibrio parahaemolyticus in Australia during September 2021-January 2022. A total of 268 persons were linked with the outbreak, 97% of whom reported consuming Australia-grown oysters. Cases were reported from all states and territories of Australia. The outbreak comprised 2 distinct strains of V. parahaemolyticus, sequence types 417 and 50. We traced oysters with V. parahaemolyticus proliferation back to a common growing region within the state of South Australia. The outbreak prompted a national recall of oysters and subsequent improvements in postharvest processing of the shellfish.

Keywords: Australia; Vibrio parahaemolyticus; bacteria; enteric infections; food poisoning; food safety; foodborne illness; oysters.

Figure 1

Epidemic curve of Vibrio parahaemolyticus outbreak cases by specimen collection date, outbreak case classification, and sequence typing, Australia, September 7, 2021–February 18, 2022. ST, sequence type.

Figure 2

Phylogeny of Vibrio parahaemolyticus constructed using available pangenomes from the PubMLST database (https://pubmlst.org) and outbreak isolates of ST417 and ST 50. Data informed an investigation of V. parahaemolyticus foodborne illness associated with oysters, Australia, 2021–2022. ST, sequence type.