Passengers on board an Air New Zealand flight from Napier to Auckland last Thursday are being asked to be on the lookout for symptoms of Covid-19.
A child on flight NZ5018 who tested negative for the virus before leaving New Zealand returned a possible positive test on arrival in Japan the next day.
The family with the child had gone from Napier to Auckland en route to Japan on Air New Zealand flight NZ99.
The child also attended a Napier childcare centre, which has been alerted. The ministry of Health says the majority of parents whose children had attended the centre had been informed yesterday by the public health unit on the situation.
Health officials are treating the case as very low-risk because they suspect the child's latest result is either a false positive, or indicates an historical case, because the child had returned from overseas earlier this year.
Several close family members who remain in the country were isolated and tested, with all returning negative results.
Hawke's Bay Medical Officer of Health Nick Jones said he expected to have further test results back within 48 hours.
Dr Jones said he was working closely with the Ministry of Health, which was in regular contact with Japanese authorities, and it would provide updated information through the daily updates.
In a statement, a Ministry of Health spokesperson today said they had asked their Japanese counterparts to bring forward a second test - usually done on day six for arrivals in Japan - to verify their assessment that this was a historical case, not new.
"We have also requested a serology test of the case and the family."
All the family members who went with the child were tested before they left New Zealand - since Japan requires a pre-departure test - and all of them returned a negative result on 20 October.
The family is in managed isolation in Japan, and apart from the child, they all returned negative tests on arrival.
The ministry reiterated it suspects that the weak positive result, which was obtained from a rapid antigen test, is either a historical case or a false positive.
It said the assessment of the case was that the child was not infected or infectious prior to departure, so any risk is considered to be very low.
Passengers on that flight and parents from the daycare centre are being asked to keep an eye out for any symptoms in their family and advised to seek a Covid-19 test if they or their children develop symptoms.
The ministry says there have been cases previously reported where people return weak positive results due to a previous infection, even though they are no longer infectious.
- If you have symptoms of the coronavirus, call the NZ Covid-19 Healthline on 0800 358 5453 (+64 9 358 5453 for international SIMs) or call your GP - don't show up at a medical centre