Forty-five people, mostly over 70 were admitted to hospital with campylobacter a Hawke's Bay District Health Board update reveals.
The DHB has conducted four surveys since the event in August, the latest on September 27 and 28, the results of which they collated with the previous findings.
The surveys were conducted by telephone and the latest figures brought the estimated total number of residents affected by gastroenteritis to 5530 or 39 per cent of Havelock North's population, 1072 of those confirmed cases.
Of those hospitalised, as of October 10, 27 were aged over 70, followed by four in the 60-69 year age group, four in the 40-49 age group and three in the 50-59 age group.
Four people under the age of 20 also ended up in hospital.
The total number of people who had developed the rare complication from campylobacter, Guillan Barre Syndrome, was reported to be three people. As the incubation time was up to four weeks, it was considered that any new cases now would not be linked to the original outbreak.
Of the estimated 5530 residents who were affected, 32 per cent had a recurrence of the bug, and as of September 28 four people were experiencing ongoing symptoms.
At the time an estimated 78 per cent of people who had symptoms took time off work or school.
Although the boil water notice was lifted on September 3, 30 per cent of households continued to boil their drinking water, the survey found.
More detailed analysis was yet to be conducted, and the DHB said that may change the findings.
Late last month an initial public hearing was held as the first step of the inquiry into the Havelock North water contamination.
The DHB requested, and was designated as a core participant in the inquiry. At the second hearing, scheduled for November 28, the group will present evidence on the gastro outbreak to the inquiry.