Dr Andrew Burns, of Hawke's Bay Hospital, said the patient now in hospital had diarrhoeal symptoms during the Havelock North campylobacter outbreak last month.
He said any residents who experienced pins and needles, weakness or clumsiness of hands or feet should seek medical help quickly.
The exact cause of Guillain-Barre syndrome is unknown. But it is often preceded by an infectious illness such as a respiratory infection or the stomach flu.
In another development, more details about the Government inquiry into the water-supply contamination were announced yesterday.
The inquiry begins this week, with an initial sitting in the region in the coming weeks. It is required to report back by March 31 next year.
Hastings Mayor Lawrence Yule said he was impressed with the credentials of those on the inquiry.
"The thing we need to remember is while this has been harrowing for 5000 people, and a crisis for Havelock North ... it is significant nationally, and even internationally."
Yule said he thought the inquiry covered every aspect of the situation including how the council and the Hawke's Bay District Health Board had operated.
"I think it's pretty wide-ranging and I'm comfortable with the approach," he said.
The terms of reference state the inquiry would report on and make recommendations on matters including the cause of the outbreak and whether any person or organisation was at fault or failed to meet required standards, the adequacy of the management of drinking water supplies for Havelock North, and any changes or additions to operational practices for the monitoring or testing of drinking water.
Mackintosh said it was very good the inquiry was starting.
Although "these things do take time", she would be glad for answers around the cause of the contamination. She hoped the inquiry would look into the Brookvale bores, which supplied Havelock's water, and communication by the district health board.
Inquiry panel
Chairman: Retired Court of Appeal judge the Honourable Lyn Stevens QC
Members
NZQA chief executive and former Director-General of Health Dr Karen Poutasi
Local government and engineering expert Anthony Wilson