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.
Only non-toxigenic Vibrio cholerae were detected during a unique year in that our borders were closed for the entire period.
This is the third year that NZ has experienced an outbreak of Vibrio parahaemolyticus (VP) associated with the consumption of locally grown mussels. The 2021 outbreak strain was 7-gene multi locus sequence type ST50 – as was the 2020 strain.
However, unlike other years we also experienced a summer outbreak associated with seafood that was recreationally collected from around our coastline. Again, ST50 predominated but other sequence types were also evident.
All VP cases isolates were analysed via whole genome sequencing with the exception of two which were not associated with gastrointestinal infection – one was from an ear swab and one from a wound infection at the site of an injury sustained on an oyster shell.
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 Vibrio parahaemolyticus numbers returned to the levels expected compared with previous years suggesting that the vast majority of NZ cases are locally acquired.
Unsurprisingly there were no cases of toxigenic cholera confirmed in 2020.
There was an outbreak of Vibrio parahaemolyticus. Isolates from 23 cases clustered genomically and were confirmed as being 7-gene multi locus sequence type ST50 – an uncommonly reported sequence type in the international literature. The majority of cases consumed locally acquired raw or partially cooked mussels prior to illness.
This is the second year that NZ has seen a winter outbreak of Vibrio parahaemolyticus associated with the consumption of locally grown mussels. Whilst it could be postulated that the winter outbreaks could be associated with global warming, it must be recognised that the use of culture independent diagnostic methods which look for Vibrio in all samples, all year round, have only been introduced over the last five years and is a confounding factor.
There were no isolates confirmed as being toxigenic cholera this year. There was one isolate, which identified as Vibrio cholerae O139 but was non toxigenic.
There was an outbreak of Vibrio parahaemolyticus in May 2019. Isolates from outbreak cases clustered genomically and were confirmed as being the pandemic 7-gene multi locus sequence type ST36 strain. The majority of cases consumed locally acquired raw or partially cooked mussels prior to illness.
Historical Vibrio parahaemolyticus data is confounded in a number of ways, highlighted during the above outbreak: The organism is notifiable in NZ but only under "Acute gastroenteritis". Diagnostic laboratory detection methods vary widely; laboratory referral of isolates to ESR was sporadic. Communications during and following the outbreak have resulted in improved notification and referral of isolates.