A new strain of the norovirus stomach bug that has hit New Zealand has been linked to a death in Northland.
The Sydney-2012 norovirus strain was identified in Australia last year, and is a combination of two strains that originated in Holland and Japan in about 2007.
It is a new, highly infectious strain that can cause epidemics.
It has health officials around the world concerned and in December last year 17 outbreaks of the new strain had been identified in New Zealand, including one death in Northland.
There were 87 cases of norovirus in October and November last year, compared with 14 in 2011 and 23 in 2010, ESR senior scientist Joanne Hewitt said.
Of the 87 in October and November last year, 67 were blamed on a new strain known as the Sydney-2012, making it the predominant strain.
Northland medical officer of health Jonathan Jarman said the new strain had replaced the New Orleans strain that had been around since 2009.
Dr Jarman said of the five confirmed Sydney strain norovirus cases reported in Northland between September and last month, all were in resthomes and affected residents and staff.
He confirmed the death was that of a resthome patient.
"The feedback I have received from resthome nurses is that the Sydney 2012 strain is similar to the New Orleans strain but perhaps causes more vomiting,'' Dr Jarman said.
It is likely that many more people have been affected than just those in these confirmed outbreaks, but most people are not tested as it usually only causes a couple of days' illness in healthy people.
Dr Jarman said two deaths in Northland in 2011 were associated with outbreaks caused by the New Orleans 2009 strain so the death from the new strain was not out of the ordinary.
"Norovirus gastroenteritis is normally only a mild to moderate illness but the elderly and the very young can have more serious disease.
"In 2011 we had a large outbreak of norovirus in Northland resthomes.
"The final number of affected people with confirmed or suspected norovirus gastroenteritis was 288 with two associated deaths.''
Dr Jarman said one of the unique features of norovirus was it could spread through the air as well as through the usual ways tummy bugs spread.
"Norovirus has been described as the Ferrari of the virus world because it is so infectious and can spread so quickly. I take my hat off to any resthome that can control an outbreak of norovirus,'' he said.
Norovirus symptoms are mainly vomiting and diarrhoea, stomach pains, aching muscles, feeling off colour and a headache that usually lasted for a couple of days. He said people with symptoms of gastroenteritis were advised to stay away from other people and see a doctor if the symptoms were severe or the illness did not ease after two days.
There was no treatment for norovirus other than to let the illness take its course and stay hydrated by drinking regularly.
The most important way of preventing spread was thorough hand hygiene after going to the toilet and before preparing food.
There were more than a million cases of the new strain in the UK last year.