A Havelock North woman is in a stable condition after contracting a nervous system disorder, following last month's gastro outbreak.

LISTEN ABOVE: Hugh Pennington spoke to Rachel Smalley

The woman, in her 40s, has been diagnosed with Guillain-Barre Syndrome.

Professor of Microbiology at Aberdeen University, Hugh Pennington, told Rachel Smalley it attacks the body's nerves resulting in a loss of muscle movement.

"Its a sort of a response you make to an infection where your immune system sort of goes into overdrive."

Mr Pennington said her condition could've been worse.

"About a quarter of the people who get it, they can still walk. They are left weak but not too weak. Another quarter, it affects the chest muscles so they can't breathe so they have to be put on life support."

Hawke's Bay Hospital says any locals who get pins and needles, or weakness or clumsiness in their hands or feet, should get medical help quickly.

Resident Kerry Mackintosh was also struck down with Guillain-Barre syndrome last month and also now has reactive arthritis.

It's not known exactly what causes the syndrome but it often follows an infectious illness.