"It's a real mystery where he got it from," she said. "It's a pretty rare disease and the main concern is around pregnant women because rubella can do pretty nasty things to the fetus."
Dr Mills said awareness of the recent measles outbreak in Auckland might have made doctors more alert to the need to test for rubella, which is normally a fairly mild illness for those other than pregnant women.
"Sometimes the [rubella] rash isn't that significant and people don't think it could be rubella so it's possible there may be more cases out there," she said.
Northland health workers were checking who the man had been in contact with.
Meanwhile, a 3-year-old Ruakaka girl who was taken to hospital with suspected measles last week did not have the disease, tests showed.
Although more than 100 people were confirmed with measles in the Auckland outbreak, so far there has been only one case in Northland - a 9-year-old boy from Hokianga.
WHAT IS RUBELLA?
* Rubella, commonly known as German measles, is a disease caused by the rubella virus.
* The disease can last one to three days.
* Infection of the mother by rubella virus during pregnancy can be serious.
* If the mother is infected within the first 20 weeks of pregnancy, the child may be born with congenital rubella syndrome (CRS), which entails a range of serious incurable illnesses.
* Spontaneous abortion occurs in up to 20 per cent of cases.
* The virus is transmitted via airborne droplets from the upper respiratory tract of active cases.
* The disease has an incubation period of two to three weeks.
- APN
