Health authorities, who by then had noticed a pattern in the torrent of patients arriving at doctors' clinics and hospitals with gastroenteritis symptoms, spoke to Hastings District Council. The council, in turn, had just received a confirmed positive test back from the town's primary water supply. Bacteria - likely campylobacter - had been detected.
Officials decided to chlorinate, almost straight away. That same afternoon, the council went public on the issue, warning residents to boil water, putting out instructions on its website and Facebook page. But it was too late. Too many people had already drunk the contaminated water.
By the end of the week, an 89-year-old Havelock North woman had died and tests have concluded she had contracted campylohbacter. The Coroner's office is investigating whether the infection contributed to her death. Two other residents were admitted to intensive care in hospital and by this week, more than 3000 had sought help for the gastro-related illness. The figure is thought to be higher because hundreds more did not report to doctors or emergency rooms. Sixteen are still in hospital.
Amid accusations of inaction and poor communication - and a myriad conspiracy theories - Hastings' mayor Lawrence Yule apologised to his community. "The council is charged with supplying you safe, reliable water," a statement read. "The council has failed to do this on this occasion."
Investigations were promised. A Government inquiry was announced - not just looking at Havelock North but wider systemic issues such as whether or not there should be mass chlorination of untreated supplies.
University of Otago Professor of Public Health Michael Baker stresses the significance of what has happened to a modern-day water supply.
"Historically waterborne outbreaks were devastating - from cholera, typhoid, back 100 years - but not in modern times," he says. "This is the largest ever common-source outbreak I'm aware of in New Zealand in recent times."
Key to the follow-up investigation will be to find out how the water became contaminated and whether it could have been prevented. Experts will first need to find the type of contamination - birds, or stock run-off, or something else - and then where it came from, and how it got into the supply.
Havelock North's drinking water system is relatively complex. It comes from a shallow underground aquifer, Te Mata, which is made up of permeable gravel, with a layer of silt and clay above. The water is pumped up through three different wells from the Brookvale borefield, northwest of the town.
Previously, the supply was considered "secure", sealed off from contamination. However two previous events, in 2013 and 2015, caused a rethink of that status. In both cases, E. coli was detected at a single well, "bore 3", although no one was reported ill. After the 2015 contamination, bore 3 was closed and an investigation began into where the bacteria was coming from.
Results of that investigation were announced only this week, hurried through more than nine months after the event.
The report, by consultants Tonkin & Taylor, drew no firm conclusions but suggested a farm, Te Mata Mushrooms, near the well sites, may have somehow affected a protective layer around the aquifer during earthworks last year. Runoff from the compost the farm used may have been able to seep into the water supply, the report suggested, but the consultants could not be sure.
The report recommends further investigation to assess the potential for adverse effects on groundwater quality "including a human health risk assessment". It notes that both previous contamination events came after heavy rainfall.
Weather reports show that on August 6 - two days before the first people fell ill - Hawke's Bay was hit by rough weather, with blizzard-like conditions in the high country and, in the north of the province, three months' worth of rain falling in a weekend.
Questions have been raised about whether the council - if it had received the report earlier - may have prevented the current outbreak, firstly by identifying the source and being able to address it; and secondly by recognising the signs and being able to test the supply more frequently.
After this month's rainfall, the council was still testing twice weekly. For insecure supplies, drinking water standards require daily monitoring, particularly if there has been recent contamination.
The council is yet to answer questions about testing, or the report. It will only say the investigation was complex, hence the length of time it took to complete.
However, others say there should have been more urgency.
Water treatment specialist Iain Rabbitts says the investigation should have been top priority."If it had been me and there was contamination in what I thought was a secure groundwater source I would have been really keen to find out the cause.
"But it's easy to say that in hindsight. What you've got to remember is that they're working within the system set up by the Ministry of Health."
Rabbitts, like his colleagues at the sector body Water New Zealand, believes that even with extra precautions such as more regular testing, illness may not have been prevented - largely because it takes 24 hours to get a confirmed test back. "I think the fundamental issue is that there was always that risk. It doesn't matter if it was now or tomorrow or in 20 years time, the issue is that the standards need tightening."
He believes the only real safeguard is to chlorinate all water. It is likely any inquiry will consider whether it is time to introduce that measure.
New Zealand records about 50 waterborne outbreaks a year. Most are caused by the pathogens giardia and crypotosporidium, followed by campylobacter.
Most of the time, the numbers affected are small - on average about eight people, according to data from ESR. In 2012, however, an outbreak in Darfield, near Christchurch, saw 125 people taken ill. The cause was animal effluent entering a well after heavy rain. The water was not adequately treated.
The most famous international case occurred in Canada in 2000. Seven people from the small community of Walkerton, Ontario, died and thousands fell sick. The illness was the result of cattle manure washing into a shallow water supply well, but an investigation found multiple failures and raised concerns about the management of public water sources across the country.
A report on the contamination said "many factors contributed to the Walkerton tragedy, highlighting the need for constant vigilance and multiple layers of protection to ensure safe community water supplies".
For Baker, joining the ranks of places such as Walkerton is "not a club we want to be part of". He says the Havelock North incident raises wider questions about the way we look after our water - a resource threatened by climate change as much as the intensification of agriculture. "It is a valuable resource that we need to take care of."
The irony of the Havelock North outbreak is that the Brookvale bore system was supposed to be on the way out. Environmental reports concluded taking so much water from the aquifer was depleting the nearby Mangateretere stream, and the regional council wanted change.
Hastings District Council had been charged with finding an alternative supply before the next consenting process, and it was included in the long-term plan.
But finding a new supply was going to cost money. Mayor Yule had challenged the plan, saying he didn't understand why the council needed to "spend millions of dollars upgrading bores . . . when we're told there's plenty of water available".
"Other than doing a good thing of conserving water, I can't understand why we have to do this," he told reporters in 2013.
Ecologist Mike Joy says that attitude is exactly the kind of approach that leads to incidents like the Havelock North outbreak.
"It is just a symptom of the shit way we treat fresh water in New Zealand," Joy says. "It's sad that it's only because a whole town's got sick that people realise it." But people are constantly getting sick from shallow bores, Joy says, and scientists have been "banging on about it for years".
New Zealand has prioritised short-term savings and implemented lax policies which will only cost the country in the long-term, he says.
"We've treated water like it wasn't important and forgotten how vital it is to everyone. Maybe this will be a reminder."
