Passengers on a Bluebridge Cook Strait ferry may have been exposed to the measles virus. Photo: Supplied/ US CDC
Health New Zealand is warning a Cook Strait ferry sailing was a measles high risk exposure event with the potential for the disease to spread across New Zealand.
Public Health medicine specialist Sharon Sime told Morning Report they were assuming the worst.
They do not know who the case was on the 2-5.30pm Bluebridge Ferry sailing from Picton to Wellington on 3 October.
But four cases are now linked to that sailing.
The ferry sailing cases publicised on Thursday bring the total active number of cases nationally to six.
One of the cases is in Northland, two in Auckland, two in Manawatū, and one in Nelson.
These are all in addition to the cases reported last week in Northland and the one case in Queenstown-Lakes District.
Sime said they public health services were continuing to investigate suspected cases that they had been notified of.
"We're wanting to draw people's attention to the high risk exposure which is the Bluebridge ferry.
"We are now very confident that there was an infectious measles case on that ferry and because that sailing was on the last Friday of the school holidays it's likely that people who were on the ferry have now spread across New Zealand."
That means there could be a risk of measles no matter where you were in New Zealand, she said.
Anyone who was on that ferry and has measles symptoms, or even if they had measles symptoms which have now resolved, should contact Healthline or their health provider, she said.
Bluebridge ferry had assisted in providing passenger contact details to health officials to allow them to send out text messages and emails to passengers, she said.
But that did not include all passengers on that ferry as some people booked through other agents, she said.
Sime said they were assuming the worst, which was that there was measles but in the community with cases that were not related to overseas travel.
They were still investigating this but it was an escalating risk, she said.
The measles incubation period was 21 days, so there was still a chance that people who were on board the ferry sailing could be developing measles now, she said.
"The reason we want them to contact us, even if their symptoms have passed, is we want to make sure we're getting on top of any secondary cases."
Anyone who has measles symptoms should stay home because it prevents you from spreading the disease, she said.
Public health teams were ready to ramp up as required, she said.
"We know our vaccination workforce is pushing vaccination because as we keep saying measles is almost a completely preventable disease - if you have two MMR vaccines at least four weeks apart 99 percent of people will be fully protected from measles."
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