A general practitioner in Kaitaia says a research programme targeting rheumatic fever is likely to discover up to 20 Northland children with heart damage.
The Green Lane Paediatric Cardiac Service will begin heart scans of 600 10-13 year olds in Kaitaia next week.
Dr Lance O'Sullivan says rheumatic fever, which is caused by throat infections, is still found in low-income Maori populations.
He says similar research on the east coast and in South Auckland found 3% of children had undetected heart damage from the disease, which has the potential to destroy their health.
Dr O'Sullivan says children who have had rheumatic fever can be treated with monthly penicillin shots, saving them from heart valve replacements or transplants.