Which makes it easy for norovirus to spread, particularly if people are not fussy about washing their hands, says a University of Otago virologist specialist.
Associate Prof Vernon Ward said contracting the highly contagious virus could be as easy as touching a surface an infected person has touched and then putting your hands near your mouth.
The virus is spread by swallowing and/or breathing in droplets containing the virus from the faeces or vomit of an infected person.
The more common ways to contract the illness include consuming contaminated food and water, person-to-person via minute vomit droplets hanging in the air and by touching contaminated surfaces.
The virus is extremely tough and can survive for months outside the body, on surfaces such as walls, furnishings and light shades.
Unlike bacteria, which are free-living organisms that make their own energy and replicate themselves, norovirus needs human cells to reproduce.
A virus is simply a shell containing genetic material, which uses a human cell's own machinery to replicate itself, usually destroying the cell in the process.
Why norovirus caused vomiting and diarrhoea, researchers were not sure, Prof Ward said.
There is no treatment or vaccine for norovirus, and even research is limited, as nobody has been able to grow it in a laboratory.
Instead researchers use mouse norovirus, which they have managed to genetically engineer.
But they need a breakthrough to grow a cell culture of human norovirus, to find out if they can perform the same feat on human norovirus.
Such a breakthrough could eventually lead to a cure or vaccine for human norovirus.
Public Health South medical officer John Holmes said the importance of thorough hand washing could not be over-emphasised.
Hands should be washed after using the toilet, before preparing food, before eating food and people should avoid putting their fingers in their mouths.
