It's two years since the biggest waterborne campylobacter outbreak in the world which risked denting public confidence in the safety of our water supplies.
The outbreak caused at least one death and thousands getting sick. It is a stark reminder of how much we rely on the safety of our water supplies.
The government inquiry that followed highlighted a number of steps water suppliers could take to better protect those water resources.
Environmental Science and Research, the organisation that I lead, has a lot to do with drinking water.
We monitor standards and are also involved in the identification and tracking of pathogens like campylobacter, which was the cause of the Havelock North gastroenteritis outbreak.
Each year ESR scientists prepare a report for the Ministry of Health surveying networked drinking water supplies serving populations of more than a 100 people.
To meet standards, water suppliers have to address two key components; one covering the quality of the water and another related to the sampling requirements.
Drinking water contaminated by bacteria from humans or animals poses the greatest risk of disease.
The detection of an indicator organism in the water such as E. coli shows that water has been in contact with faecal matter, indicating the possibility of pathogens, which a water supplier needs to respond to.
In the Havelock case, finding E. coli in water samples was the first step in the process of identifying contamination to the supply which was ultimately traced to livestock near one of the bores.
In that case our scientists were able to obtain a water sample during the early stages of the event that contained campylobacter which they could definitively link to the cases of illness being experienced by local residents.
In many water contamination cases, we may not realise there is an issue until after the contamination event has passed.
Then there are the delays between consuming the water and people getting sick – from 1 to 10 days depending on which organisms are there.
So before water suppliers even realise they have a problem, that contamination is no longer there and scientists are left trying to re-establish conditions that were similar to the time of the event.
A confusing factor is that there are many potential sources of contamination such as from a range of livestock to leaking septic tanks and sewage pipes.
Another challenging factor is that we have an incomplete understanding of how pathogens like campylobacter travel through the groundwater system and how long they survive.
New research from one of our groundwater scientists has shown that campylobacter can survive in the groundwater system for two weeks, making the tracking of these pathogens even more challenging.
We have come a long way in our understanding of groundwater.
I am hosting a public event at the East Pier Hotel in Napier on October 24 that looks at the research done by our scientists since the Havelock North outbreak to improve the quality and quantity of our groundwater.
But we cannot stop here, drinking water supplies continue to be vulnerable in parts of New Zealand, especially in smaller communities where there are less resources to maintain the multi-barrier approach.
This is the just the beginning of our journey and there is still more we need to know to help protect the resource for future generations.
A microbiologist in our team recently commented that the Havelock North event was a terrible event from which some very important and useful science emerged.
We can only hope that those lessons can be learnt and implemented and there will not be another death linked to waterborne illness.
* Dr Keith McLea is the chief executive of ESR