The Yersinia pseudotuberculosis outbreak
Yersinia pseudotuberculosis is a bacterium that can cause fever and abdominal pain and, less commonly, diarrhoea, reactive arthritis or rash.
It is rare in New Zealand but in September/October of 2014 more than 300 cases of yersiniosis were notified in EpiSurv, the real time web-based database operated by ESR on behalf of the Ministry of Health that captures the surveillance of notifiable diseases in New Zealand.
Cases were notified mainly from the Auckland, Canterbury, Wellington, Waikato and Bay of Plenty/Lakes regions and signaled the biggest outbreak of Y. pseudotuberculosis to date in New Zealand, with a final count of 220 confirmed cases in the outbreak.
ESR was able to support the Government response to the outbreak through the expertise contained in separate but connected teams.
ESR’s Enteric Reference Laboratory team reported the increase in the number of Y. pseudotuberculosis cases compared with the previous year and used advanced reference methods to determine that the cases were most likely associated with a common source.
Our Health Intelligence team worked with the Ministry of Health and Ministry for Primary Industries on a complex supply chain picture to identify common exposures (like farms, food, restaurants, water), and then subsequently potential food products and the likely retailers where these were sold.
ESR analysis of a shotgun questionnaire developed for Public Health Units identified fresh produce as a likely vector for the outbreak, specifying exposure to lettuce and carrots as having significant odds ratios.
As is usually the case in outbreaks of this nature an exact source of contamination was unable to be identified but ESR was able to provide lead agencies with a robust intelligence picture and expert analysis of trends and response options.