NSW rotavirus outbreak worst in five years

Health officials are scrambling to find out if a mutant strain of a gastro virus is behind a surge in outbreaks in children and the elderly across NSW.

Rotavirus is a common cause of gastroenteritis for babies and preschool children and is passed from person to person by touching contaminated hands or faeces.

More than 1300 cases of the highly contagious virus have been recorded by NSW Health this year, with 412 of these recorded last month - the worst outbreak since 2012.

The health department is exploring why the virus hit with such a vengeance this year, saying it may have mutated - making more people susceptible to infection.

Despite a surge in infant vaccinations against the virus, the vaccine is only 70 per cent effective in preventing infection.