What is it, how does it spread and what can New Zealand do?


More than two years into the Covid-19 pandemic, new variants continue to emerge and it’s often not immediately clear what kinds of benefits – if any – the virus gives or how many people should to worry.

This is the case for the XE variant of Omicron. Although there are more and more people contracting it abroad and New Zealand discovered its first case on Saturday, scientists say much about it is still unclear.

Here’s what we know so far.

What is Omicron XE?

University of Auckland computational biologist Dr David Welch says XE is a “recombinant” virus – made up of genetic material from multiple sources.

He says the variant appeared because someone simultaneously contracted the BA.1 and BA.2 subvariants of Omicron. The genetic material of the two variants created the hybrid during an error in the process of copying the virus. This makes it different from the likes of Delta or Omicron, which emerged through mutation.

Although it was a hybrid of the Omicron BA.1 and BA.2 subvariants, with the latter about 30% more transmissible than the former, Welch says how they combined was random. .

“You can think of a virus having a genome that is an instruction manual for the virus, if you like. It’s basically a chain letter.”

During the recombination process, these strings are randomly cut and joined, he says. Sometimes the configuration does not work. In the case of XE, the genetic code was viably combined.

The World Health Organization (WHO) has not yet classified it as a variant of concern or assigned it a Greek letter.

“XE belongs to the Omicron variant until significant differences in transmission and disease characteristics, including severity, can be reported,” the WHO said in March.

More than a dozen recombinant strains of the SARS-CoV-2 virus have been classified to date.

Does XE cause more serious disease?

This is early days and “there is no evidence at this time” that this is the case, Welch says.

“XE is not widely available all over the world at the moment, so the data on whether it causes more disease just isn’t available yet.”

But he says that because it’s a hybrid of BA.1 and BA.2, the disease XE can cause will likely be similar to those.

Omicron also tends to cause less severe disease than previous variants, but spreads more easily.

Is XE more transmissible and how do we know?

Early UK modeling estimates indicate that XE, first detected in the UK in January, may have a 5-10% higher growth rate than the BA.2 Omicron variant. Growth rates are calculated by comparing the prevalence of the new variant in the number of infections in a sample of the population against another circulating variant.

But the WHO warns that the results need to be confirmed because there are so few XE infections that it is difficult to draw firm conclusions. Welch says it’s also not “clear” if the UK spread of XE will be replicated elsewhere.

The UK Health Security Agency notes that XE received most of its genetic code from BA.2, including the spike protein the coronavirus uses to invade host cells.

Therefore, this may mean that the transmissibility and severity of XE ends up resembling that of BA.2. This also means that people’s protection against XE – derived from previous infection or from Covid-19 vaccines – does not appear to be significantly reduced compared to the previous subvariant.

What should we do now that XE has been discovered in New Zealand?

“I think if [XE] is a bit more transmissible, we might see that it might produce a slightly longer tail to this outbreak,” Welch says.

But, he adds that other factors, such as winter favoring the spread of respiratory viruses and the easing of pandemic restrictions, will likely drive the number of cases “much more significantly than XE”.

Deputy Prime Minister Grant Robertson told Breakfast on Tuesday that New Zealand is ready for XE.

“What we have in place for other variants will still work with respect to this new variant,” Robertson said of the current public health measures.

Michael Baker, a professor and epidemiologist at the University of Otago, says vaccination remains the best defense against XE and other new variants of Covid-19.

Should we continue to pay attention to new variants? Why?

Welch says it’s important to keep an eye out for new variants of concern in case they might evade current vaccines or reinfect people.

“Every time a major new variant has dangerous characteristics, we might have another wave. So the sooner we know about any new variants…the better we can prepare for them.

“Preparing for that might involve going back to red metrics level or something.”

Immunologist Graham Le Gros warns that although rare, some people can be re-infected with Covid-19 as new variants continue to emerge.

Is New Zealand doing enough to detect new variants?

Welch told the NZ Herald earlier in April that he feared a new variant could be detected for weeks due to spotty sequencing and genomic monitoring – but that has improved in recent weeks. , with more borderline cases being genomically sequenced.

He says there is still room for improvement.

“The gold standard of genomic surveillance is to test everyone at the border, everyone who goes to the hospital and tests positive for Covid, and then surveillance testing in the background where we have sort of system where a random proportion of people who report a positive RAT get sent a [PCR] swab in the mail [for genome sequencing].”

Welch says sequencing at the border will give authorities a better idea of ​​what new variants might exist, and additional testing at hospitals can pick up those that may not have been picked up during this process and help understand. which variants cause more severe disease.

New Zealand is currently prioritizing genomic sequencing for border cases; suspected reinfections; high risk groups; or unusually serious illnesses, especially when the person has been vaccinated.

DHBs are also asked to send randomly selected PCR positive swab samples to the lab. This aims to provide a representation of how Covid-19 was spreading between different locations, age groups, ethnicities and socio-economic levels.

1News has contacted the Department of Health for comment.


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