Auckland's measles outbreak has spread to ambulance workers, with at least one St John medic struck down with the highly contagious viral disease.
St John has confirmed that one of its Auckland staff has measles.
St John's spokesperson Sarah Martin said the case was diagnosed at the end of last week but said the worker was not sick enough to be admitted to hospital.
Martin said the organisation had had "a small group of staff members off sick with suspected measles", but that list fluctuated daily with just one at present.
Some staff have been quarantined because they were in close contact with people who have had measles.
"We are organising testing for them to clarify their immunity status.
"St John is also working on a process for determining measles status of all St John clinical staff members, as well as working on an immunisation campaign for all staff without immunity to measles."
Staff have been sent a warning to all workers to wear gloves, masks and disposable overalls when treating anyone with measles after one person on staff contracted the disease.
"We follow best practise including cleaning of ambulances after every patient who may be carrying an infectious disease."
The warning comes as the number of confirmed cases of measles in Auckland in the past four months climbs to 179.
Of these, 26 people have been admitted to hospital.
St John said it will keep the extra checks in place until the measles outbreak is under control.