Human Salmonella Isolates, 2021

The number of Salmonella isolates confirmed this year (n=668) showed a decrease in comparison with 2020 (n= 726). This decrease is most likely due to a reduction of imported cases as a result of NZ's closed border COVID-19 containment strategy.

Salmonella Typhimurium ST19 was the predominant type, representing 22.3% of total isolates. 5-SNP clustering of all cases showed this to be a diverse group.

The main Salmonella serotype showing an increase this year in comparison with 2020 was S. Enteritidis (from 9.9% to 19.3%). This was due to two separate events:

• A cluster of 28 cases of Salmonella Enteritidis ST183, locally designated 5-SNP cluster type _2021_C_01, which was detected in January and February 2021 and predominantly dispersed within the South Island. A common food source was not confirmed.
• Forty-nine cases adding to the Salmonella Enteritidis ST11 locally designated 5-SNP cluster type _2019_C_01. The cases were geographically dispersed and a source for the outbreak was confirmed as being from the poultry industry.

Salmonella serotype showing a decrease this year in comparison with 2020 included: S. Typhi (from 3.6% to 0.4%). This can be wholly attributed to closed borders.