Some young children had been admitted to the hospital for a day or two to receive intravenous fluids to treat dehydration, he said.
"With a large number of ulcers in the mouth, despite good pain relief they don't drink well and can get dehydrated."
Human hand, foot and mouth disease is unrelated to foot and mouth disease in animals.
It typically causes outbreaks of mild illness in young children at early childhood centres and schools in spring and autumn. It is spread by contact with the fluid in the blisters, and with Nasal and throat secretions. The virus is also present in faeces.
Symptoms include mild fever and a sore throat, followed by ulcer-like blisters in the mouth and a rash with small fluid-filled blisters on the fingers, palms and the soles of the feet.
However, the current outbreak, from a less-common strain of the virus that causes the disease, leads to a much more extensive rash and, in some cases, the shedding of nails some weeks later. Some adults have been affected.
Health authorities say transmission of the virus can be reduced by good hygiene, including washing and drying hands well, and disinfection of surfaces in childcare centres and homes with bleach.
The Health Ministry advises keeping children away from childcare and school until their fever is gone and their mouth sores have healed.
Jill Oliver, the centre operations manager for Toddlers Turf Childcare Centre in Manukau, said six children and one teacher from the centre were away sick with the disease.
She said it could be difficult for working parents to keep children home, but they accepted it was important to control the spread of the illness.
ProCare clinical director Dr John Cameron said two child patients of his Westmere general practice had recently caught the disease, which could make children miserable. He recommended keeping fluid intake up and giving paracetamol and ibuprofen for pain relief and fever.
"That will reduce down some of the sting, but cuddles are the best treatment."
