Hawke's Bay's water problems might not be over, with fears a wave of illness caused by cryptosporidium and giardia is to come.
Hospital admissions rates are returning to normal and schools are open again, following the contamination of the Havelock North water supply with bacteria campylobacter. About 4500 have fallen sick over the last two weeks, about a third of town's entire population.
While it only takes a few days for campylobacter to make a person sick, Hawke's Bay District Health Board chief executive Kevin Snee says it can take up to 20 days for cryptosporidium to make its present felt.
"The exposure probably occurred starting on the sixth or seventh of August, so we're 16 or 17 days in," Dr Snee told Paul Henry on Tuesday morning.
"You might expect cryptosporidium to be appearing, so people starting to develop another wave of sickness. We haven't actually found that yet, but there's still up to 20 days when it can occur.
"Obviously if it's in the water, it may still be there until we fix the Havelock water permanently."
Cryptosporidium is highly resistant to chlorine, so residents need to keep boiling their water until it's given the all-clear - which could take some time.
"Cryptosporidium can be difficult to isolate."
Dr Snee says residents shouldn't be complacent if they're already been sick - fighting off one infection doesn't make you immune from another.
But if there is a second wave of illness, based on how they handled the campylobacter he's confident the local hospitals can cope.
"The hospital has not been overwhelmed. The hospital could so easily have been overwhelmed had it not been for the great work in the community."
The Government has announced an inquiry into how the water got contaminated, how local health authorities responded and what improvements could be made to ensure it doesn't happen again. Dr Snee has some ideas already.
"We need to revise the testing regime that we have. We need to have a good look at the way we regulate the water supply, because I don't think it seems to be adequate."
The Government's inquiry, which will report to Attorney-General Chris Finlayson, won't look into questions of civil or criminal liability. That job will fall to the council or the police, says Prime Minister John Key.
The Green Party says the Government should use the opportunity to look into how "land use and water management contributes to E. coli and waterborne disease contamination".
"Disease-causing E. coli and campylobacter bacteria have been reported in water supplies in other parts of the country in recent years, including Patea, Hanmer Springs and Christchurch, in addition to the outbreak in Havelock North," says water spokesperson Catherine Delahunty.
"The Government should take this opportunity to assess how land use affects drinking water supplies. Instead it's avoiding looking at the real causes of pollution.
"National seems to think that if they look at sources of pollution they might not like what they find, and their strategy of exploiting the environment for short-term gain will come under scrutiny."
One person died in the outbreak, an 89-year-old woman. A post-mortem showed as well as having campylobacter, she also had other underlying health problems.