Yersinia isolates

Yersinia isolate data from ESR's enteric reference laboratory.

We welcome the use of this surveillance data with the following acknowledgement, 

New Zealand surveillance data provided by ESR, funded by the Ministry of Health with the cooperation of the diagnostic laboratories.


The last five years of data is available here. Yersinia isolates data from 2017 - 2008 can be found in the Archive.

A comprehensive review of Yersiniosis in New Zealand was published by ESR staff in Pathogens in February 2021.

You can read more about ESR's work on Yersiniosis here.

  • 2021

    2021 - Yersinia isolates

    Yersinia case isolate numbers were higher this year than any other year in our records.

    Yersinia enterocolitica biotype 2/3 serotype O:9 continues to dominate as the causative agent of NZ yersiniosis.

    Selected isolates have been sequenced as part of surge investigations and for projects such as the ESR-led, HRC-funded three-year study Unravelling the mysteries of yersiniosis commenced in 2021.

    Common bioserotypes continue to be associated with specific McNally 7-gene multi locus sequence types:

    Yersinia enterocolitica biotype 2/3 serotype O:9 ST12

    Yersinia enterocolitica biotype 2/3 serotype O:5,27 ST14

    Yersinia enterocolitica biotype 4 serotype O:3 ST18

  • 2020

    2020 - Yersinia isolates

    The year 2020 has been unusual at best for everyone and the enteric data for 2020 will always stand apart from other years due the multiple effects of our COVID 19 response on our national data.

    When NZ locked down at the end of March 2020, diagnostic laboratories staff and resources were given over to the task of establishing and performing testing for COVID 19. Therefore, diagnostic laboratories were actively discouraging referral of other, more routine work. This coupled with people staying home in small bubbles; not eating out; and not being able to readily access face-to-face medical assistance meant that for a period of two months there were very few enteric pathogens received at ESR for typing.

    Once NZ moved back to Alert Level 2, enteric testing and isolate referral gradually recommenced and Yersinia numbers returned to the levels expected compared with previous years suggesting that the vast majority of NZ cases are locally acquired.

  • 2019

    2019 - Yersinia isolates

    Yersinia data has been confounded in a number of ways for 2019:

    • Laboratories servicing 50% of NZ are no longer testing for Yersinia pseudotuberculosis, as the target is not in the multiplex PCR kit they have chosen to use.  Therefore, when we noted an increase in this species during September 2019, this increase was difficult to quantitate and investigate. Genomic analysis of available isolates indicated cases did not all conform to a single cluster type and were therefore unlikely to be from a common source.
    • A laboratory testing 1/6 of the NZ’s samples ceased referral of Yersinia isolates in November 2018 and has not resumed this referral.

    The ongoing increase in Yersinia cases in NZ, is real and sustained and is due to the emergence of biotype 2/3 serotype O:9.

    The Enteric Reference laboratory introduced serotyping of Yersinia enterocolitica biotype 1A in September 2019. ESR is only screening with a small number of antisera and organisms not conforming to a specific serotype are being reported as being not O3; O5; O8; O9. This designation will comprise a heterogeneous group and is not in itself a type.


  • 2018

    2018 - Yersinia isolates

    Yersinia enterocolitica (YE) biotype 2/3 serotype O9 remains the most commonly identified type, accounting for 56% of confirmations followed by YE Biotype 1A and YE biotype 4 serotype 3 each accounting for 19%.

    The pathogenicity of Biotype 1A continues to be researched internationally.

    Confirmations of Yersinia pseudotuberculosis have decreased annually since 2014 when there was a large outbreak involving 220 confirmed cases [ref: ] Williamson DA, Baines SL, Carter GP, da Silva AG, Ren X, Sherwood J, Dufour M, Schultz MB, French NP, Seemann T, Stinear TP, Howden BP. Genomic Insights into a Sustained National Outbreak of Yersinia pseudotuberculosis. Genome Biol Evol. 2016 Dec 1;8(12):3806-3814. doi: 10.1093/gbe/evw285. PMID: 28173076; PMCID: PMC5521734. In 2018 there were 15 isolates confirmed; however, the low number of identifications maybe due to two laboratories collectively testing up to 50% of the population now using a culture independent diagnostic method which does not detect this species.

    NZ Yersinia typing studies have recently been published:

    Strydom, H., Wang, J., Paine, S., Dyet, K., Cullen, K., & Wright, J. (2019). Evaluating sub-typing methods for pathogenic Yersinia enterocolitica to support outbreak investigations in New Zealand. Epidemiology and Infection, 147, E186. doi:10.1017/S0950268819000773




  • 2017

    2017 - Yersinia isolates

    During 2017 the Enteric Reference Laboratory undertook a method review and as a result:

    • Yersinia enterocolitica biotypes 2 and 3 are now being reported as a combined group (based on whole genome sequencing analysis)
      • From September 2017 onwards Yersinia enterocolitica biotypes 2 – 4 are being serotyped

    Overall Yersinia numbers have continued to increase and over the last the three years we have seen a significant shift with Y enterocolitica biotype 2/3 now accounting for 67% of all notifiable yersiniosis confirmations. Our historically predominant type - Y enterocolitica biotype 4 – now accounts for just 11%.

    The pathogenicity of Biotype 1A remains the subject of international debate. It is notifiable in NZ and in 2017 accounted for 21% Y enterocolitica confirmations.

    Following the large outbreak of Yersinia pseudotuberculosis in 2014 numbers have fallen to just 12 confirmations for the year.