They could also phone Whangarei Hospital.
The virus usually takes 10 days to make itself felt so the first cases could have appeared on Monday.
Northland medical officer of health Clair Mills said no one had reported symptoms as of Thursday afternoon. She was hopeful Northlanders had not been exposed to the virus.
Most completed the race early in the morning while the infected firefighter climbed the tower later in the day.
Measles was taken seriously because it was highly infectious and could lead to life-threatening complications such as pneumonia.
Of the six Hokianga residents infected last year, two ended up in hospital.
The Fire Service and its volunteers had been cooperative, Dr Mills said.
The Waipu brigade dedicated their climb to local leukaemia patients Barclay Morunga, 5, and Sandra Bogart.
Barclay spent the day at the Sky Tower so his mother was also contacted and given medical advice.