Vibrio Isolates 2020

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 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.