Health workers in Kaitaia are finding a higher than expected rate of strep A infection in local children - just days into a rheumatic fever prevention programme.
A team from Te Hauora o Te Hiku o Te Ika began swabbing the throats of school pupils last week to see if they have the bacteria that can cause heart damage.
Team leader Waka Williams says four out of 75 Kaitaia children tested positive for strep A - and though it's early days, that's more than expected.
Mr Williams says none of the four had symptoms at the time they were swabbed but a couple began developing sore throats soon after.
All are now on antibiotics to stop the bacteria damaging their hearts.
Rheumatic fever is still rife in parts of New Zealand with high Maori and Polynesian populations, but a throat-swabbing programme pioneered in Kaeo has effectively wiped out the disease in that community, and it's now being trialled in other high-risk areas around the country.