Two other people who tested positive and completed isolation at the Pullman Hotel at the same time as the Northland case are currently being investigated. Photo / Peter Meecham
A virologist says it is too early to say whether the presence of the South African variant was an additional factor in new Covid-19 cases just identified in the Auckland community.
The two people – an adult and a child – tested positive even though they tested negative twice while in controlled isolation and released into the community.
The couple, who had completed controlled isolation at the Pullman Hotel at the same time as the Northland Community fell, were asymptomatic and had previously returned two negative tests.
They were also shown to have the same South African variant called B.184.108.40.206.
The Director General for Health, Dr. Ashley Bloomfield previously said there is little epidemiological data available on the strain, but there is evidence that it is more contagious.
“What we do know so far is that it may be more transmissible, but that’s not as clear as the information on the variant that was first identified in the UK,” he said.
“There is evidence that this variant can bypass some aspects of the body’s immune response.”
Otago University and ESR virologist Dr. Jemma Geoghegan said it was difficult to say whether this variant played a special role in the transmission within the hotel because there were so few cases.
“We know that this variant, from which it spreads in South Africa, for example, is 50 percent more transferable,” she said.
“But in our case, it is too early to say whether it is or not [breach] was due to the new variant or to leaks [managed isolation and quarantine] Procedure. “
The Ministry of Health said it had to be confirmed whether the new cases were recent or historical infections.
When asked how it was possible that the previously tested cases were negative, Geoghegan said it was possible that they might have contracted the virus towards the end of their stay.
“It may or may not have been after the day 12 test, but it was definitely not at detectable levels when they took the test.”
The cases were described as “weakly positive” – but Geoghegan pointed out that the virus’s RNA was intact enough to generate genomes that revealed the genetic makeup of the samples.
“Weak positive” are more likely to be those samples from which very little virus can be extracted, either because of the low viral load of the infected person or simply because of the way the sample was handled.
RNA was a fragile molecule that could degrade quickly when damaged by light, heat, and chemicals – and this was to be expected in samples, even when handled and stored under ideal conditions.
Otago University and ESR virologist Dr. Jemma Geoghegan said it was difficult to say whether the South African variant was playing an additional role in the recent cases of the transfer. Photo / supplied
Still, scientists can often build genomes from samples with low RNA levels by extracting and sequencing the material multiple times.
It was also expected that serological testing of the new samples would give officers a clearer picture of how the infections occurred.
This test measured antibodies the body made in response to infection and it generally took 10 to 14 days after initial exposure to the virus for someone to test positive for them.
“This means that if someone has been infected in the past few days they are less likely to be serologically positive,” said Auckland University immunologist Dr. Nikki Moreland.
“So serology tests could be another piece of the puzzle in determining the infection timeframe for these cases.”
Twelve people also tested positive between December 30th when the Northland woman arrived and January 25th at the Pullman.
All of these cases were referred to the Jet Park Hotel quarantine facility.
Infectious disease expert at Otago University, Professor David Murdoch, said the emergence of new variants on our border must also be placed in a global context.
“If you look at where people are from – and what kind of mixing is happening around the world, even in the Covid era – the chances of new varieties coming to New Zealand are pretty high.”
Murdoch said the higher risk factor that came with these variants underestimated the importance of the tough measures New Zealand had taken to secure the country against Covid-19.
“This should only reinforce the rigorous approach we are definitely taking here.”