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More infectious variants of Covid-19 could be circulating undetected globally, says Kiwi virologist

There may be more variants of Covid-19 spreading undetected across the globe, potentially increasing transmission rates, a New Zealand virologist is cautioning.

As Covid-19 continuously evolves and spreads across the world in alarming numbers, new variants are also evolving.

“It is possible that there are new variants arriving that increase the transmission of the virus from other locations that we don’t know about yet,” says Dr Jemma Geoghegan, a virologist from the University of Otago.

The more a virus spreads the more opportunities it has to mutate and when these mutations occur one or several times over it is referred to as a variant.

“The vast majority of variants (mutations) do not seem to have any effect on transmission or any other function of the virus,” says Geoghegan.

However, there is some concern over new variants such as the ones discovered in the UK, US and Brazil in recent weeks, which appear to make the virus more contagious.

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These variants of the virus are detected through ongoing pathogen genomic surveillance, such as what’s done in New Zealand, says Geoghegan.

“These variants were detected because they happened to be at high frequencies in countries that are also doing a lot of genomic sequencing of SARS-CoV-2.

“After we have a genome, we can look for those signature mutations in the genetic sequence to classify it into a certain lineage.”

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Although these new variants don’t seem to effect the severity of the disease, other unknown variants could disrupt vaccination efforts.

This threat is one the World Health Organization is all too aware of as it urges for more genomic sequencing of the virus.

“More and more [variants] will be reported,” Dr Maria Van Kerkhove from the World Health Organization said during a press conference on the weekend.

“We are looking at different ways in which we can enhance sequencing around the world so we can detect changes in the virus.”

Kerkhove said that even with more transmissible variants popping up it’s still communities not following WHO advice on controlling outbreaks, and people not physically distancing, that is spreading the virus and giving it more opportunities to mutate.

Because there could be a number of unknown variants out there, Geoghegan says every positive case entering New Zealand at the border should be treated as highly infectious.

“It is possible that there are new variants arriving that increase the transmission of the virus from other locations that we don’t know about yet. So, we need to treat every case as highly contagious and do so appropriately.

“There are many countries around the world that haven’t prioritised genomic sequencing so we wouldn’t know if a new variant of concern has evolved there.”

Mutations of Covid-19 not new to New Zealand

Geoghegan says 75 per cent of Covid-19 cases in New Zealand’s biggest outbreaks had the now most common of variants - the D614G mutation.

“There is some preliminary evidence that the variant of the virus that has the D614G mutation increases viral load and so might increase transmission.”

This mutation is the dominant version of the virus globally and was detected just a couple of months after Covid-19 was discovered in China, the Associated Press reports.

“We are continuing to do genomic surveillance in New Zealand,” says Geoghegan.

“But without a big community outbreak we wouldn’t know if new variants are changing the way the virus behaves since you need a lot of data to make those conclusions.”

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NZ to require pre-departure Covid-19 tests for most countries starting next week

To combat the new variants from spreading in the community the Government has introduced new rules which require all returnees from countries except Australia and the Pacific Islands to test negative 72 hours before boarding a flight to New Zealand.

Although it’s another layer of protection against the new variants of the virus, the pre-departure tests aren’t going to stop the virus in all its forms coming to New Zealand, warns Geoghegan.

“If you’ve tested negative, it doesn’t mean you’re negative.

“If just means there’s not enough virus to be detected at that point in time.”