UK variant may force MIQ rethink
Tests of patients with variant showed they had more of the virus, and for longer, than those with other strains
Early indications that the more-transmissable UK Covid variant may cause a longer infection time — pushing the very limits of our quarantine period — warrants close attention, a virologist says.
And New Zealand may be an ideal place to explore that concerning possibility, with larger clinical studies using infected travellers.
A new US study has suggested it wasn’t just a higher “viral load” in infected people that made the B.1.1.7 variant at the centre of Auckland’s Valentine’s Day cluster more easily spreadable.
Rather, the results, published ahead of peer review, indicate the variant may cause longer infections of Covid-19 — and also stretch out the contagious period.
They found this period with the Sars-CoV-2 virus could be stretched to 13 days — or even as long as 16.5 days, according to the study’s confidence interval.
Travellers arriving in New Zealand, along with any detected cases or close contacts, are required to quarantine or isolate for 14 days.
The research drew on results from a small sample of 65 infected National Basketball Association (NBA) players, of whom seven contracted the B.1.1.7 strain.
“For individuals infected with B.1.1.7, the mean duration of the proliferation phase was 5.3 days, the mean duration of the clearance phase was 8.0 days, and the mean overall duration of infection was 13.3 days,” the researchers reported.
“These compare to a mean proliferation phase of 2.0 days, a mean clearance phase of 6.2 days, and a mean duration of infection of 8.2 days for non-B.1.1.7 virus.”
The researchers also found that the peak viral load of patients with the variant was slightly higher than that of players with other strains — meaning they had more of the virus, and for longer.
“This extended duration may contribute to B.1.1.7 Sars-CoV-2’s increased transmissibility.”
Research suggests the UK variant is 50 per cent more transmissible — and could also be associated with a slightly higher risk of death.
Covid-19 modeller Professor Michael Plank, of Canterbury University and Te Punaha Matatini, said the preliminary findings couldn’t be considered concrete, but raised “something to keep an eye on”.
“The biggest thing that we know about these variants is their documented effect on transmission,” he said.
“An average infected person passes the virus on to more people — and this is the main thing that makes them more dangerous.”
ESR and Otago University virologist Dr Jemma Geoghegan agreed the sample size of the latest study was notably small, and it was difficult to draw solid conclusions.
“Still, the difference between these seven samples and the others were quite shocking, as the duration of infection changed quite substantially,” she said. “This is relevant to New Zealand, because if the duration of infection changes to 13.5 days, our systems for managed isolation and quarantine (MIQ) potentially may not be adequate.”
Geoghegan stressed that further, and larger, studies would be needed to confirm the US group’s finding.
She said the only reason it came to light was because the US players were tested daily, using the same PCR-based methods scientists here used to confirm and sequence cases.
“You don’t usually test people on a daily basis — or test people again once they’ve been found to have the virus. There are no doubt many people trying to understand these patterns, but [that] remains very hard to do.
“Here in New Zealand, we actually do have the opportunity to do it, because we have a controlled environment. If people in MIQ were willing to provide daily samples once they’ve tested positive with the variant, perhaps we could.”
It was unclear whether future variants of the Sars-CoV-2 virus would keep pushing out infection periods.
“It’s a good question, but we really just don’t know.
“We’ve actually never studied a virus before in so much detail to recognise when the duration of infection is changing, like we’ve seen here.”
Answering these questions, she said, would be crucial to designing effective vaccines.
“If any of these variants can escape the vaccines, that means we might need new ones to save the whole population being put at risk again.”