Health NZ is playing down fears of a cryptosporidium outbreak after hundreds of cases were reported around the country since the start of the year.
It has prompted the agency to issue a health warning after 262 cases of cryptosporidium (or 'crypto') since the start of the year through to March 8.
Dr Susan Jack, National Clinical Director for Protection at Health New Zealand, said that is more than three times the average of 81 cases for the same period over the last five years - prompting reminders about the importance of good hygiene.
There is currently no suggestion of a major cluster or concentrated outbreak, or any link to contaminated drinking water, which caused last year's Queenstown outbreak, according to Dr Jack.
"What we can say, is that in approximately half the cases where information is available, those who became unwell with symptoms had been involved in swimming-related activities - with the majority of cases overall happening in urban areas, particularly within the Auckland, Canterbury and Waikato regions," Dr Jack said.
Crypto is a parasite found in the gut of infected people and animals that can cause smelly, watery diarrhoea and stomach cramps. It's passed on in the faeces (poo) of infected humans and animals, according to Health NZ.
People become infected when they swallow the parasites, usually in contaminated drinking water, or in shared water such as swimming pools. It can spread by contact with infected people or animals - including cattle, sheep, dogs and cats. It can also spread from infected people's hands to surfaces, toys, food and water.
Dr Jack said these cases highlight the importance of people not using swimming pools, splash pads, rivers, lakes and beaches for at least 14 days after they've had diarrhoea or other crypto symptoms.
People are also urged to keep up with other public health advice, including good hand hygiene to prevent spreading the bug to others.
"This means washing your hands with soap and water for at least 20 seconds and drying them thoroughly with a clean towel every time you go to the bathroom and before preparing food," Jack said.
"Good hand hygiene is also important after contact with animals, after gardening, when caring for someone with diarrhoea and when caring for a baby or changing nappies."
Crypto is a common cause of acute diarrhoea in children, so it's especially important children are kept home if they're unwell and also wash their hands regularly.
Dr Jack said swimming areas can also be a cause of illness if they are contaminated by sewage or animal faeces.
"To avoid getting crypto, people should check water quality monitoring warnings before jumping in the water," Dr Jack said.
"Land Air Water Aotearoa (LAWA) has information for the whole country, while those in the Northern Region can visit www.safeswim.org.nz to check local water quality."
A similar increase in crypto cases has also been reported recently across the ditch by Queensland, New South Wales and Victorian health authorities. The recent warmer weather and increased levels of swimming in recreational water have been identified as contributing factors.
The agency has increased disease surveillance across the country to closely monitor crypto notifications and the spread of the disease but at this stage, there is no risk from public drinking water supplies.
