THE message from scientists at the UK's Health Security Agency on Thursday night is that we will know very soon - probably in the space of two to eight weeks - just how serious this latest Covid variant is.

Whether B.1.1.529 (or 'Omicron') "cancels Christmas" here depends on a few things.

No cases have yet been detected in the UK but the experiences of Australia and New Zealand with Delta tell us that border controls can only do so much for so long - so the question is really when will it get here, and can we contain it?

HeraldScotland: Log scale showing rapid rise in Covid cases per million per day since November 14Log scale showing rapid rise in Covid cases per million per day since November 14

The UK is a world leader in genomic sequencing - processing around 70,000 Covid samples a week - so when it arrives it will probably be picked up quickly.

Like the Alpha (Kent) strain which took a wrecking ball to last year's festivities, Omicron is characterised by a distinctive marker known as an S-gene dropout - something not found in the currently dominant Delta variant - so if it does start spreading here it will be easy to track.

Whether it takes off - or just bumps along at a low level as other non-Delta strains have done this year - depends on a combination of its transmissibility and how well it can evade existing population immunity, whether vaccine-induced or naturally acquired through prior infection (or a combination of both).

READ MORE: Vaccine passports will not be extended to hospitality and leisure venues - for now

Right now, the signs are not good - but it is still very early days.

In my experience, it is unusual for scientists - especially those employed in official agencies such as the UKHSA - to be so forthright in expressing alarm at this stage.

More commonly they would downplay, or at least be very cautious, in describing the potential threat.

Instead they have been brutally frank with journalists: there is "great cause for concern"; the spike protein, with its 30 mutations (twice that of Delta) is "dramatically different" from the Wuhan strain on which all current vaccines are based; it is, quite simply, a "dramatic change from everything we have seen previously" and "the worst variant so far".

HeraldScotland: The UK currently has a much higher incidence of Covid than South Africa, which is in summertimeThe UK currently has a much higher incidence of Covid than South Africa, which is in summertime

On transmissibility, preliminary data from South Africa paints a troubling picture.

Until recently, the country had extremely low Covid numbers (and in comparison to the UK, and Europe, it still does).

But it has gone from reporting 312 cases as recently as Monday of this week to 2,465 by Thursday.

This has clear echoes of the experience in India, which went from being hailed as a blueprint for a herd immunity approach to stamping out the virus to the epicentre of the first Delta wave in the space of around six weeks.

Worryingly, analysis using the S-gene indicates that Omicron has taken fewer than 25 days to make up 90 per cent of the cases sequenced in South Africa, strongly suggesting that it can and will out-compete other variants; Delta took around 100 days to reach the same threshold.

 

 

Even if it had no other significant mutations - such as causing more severe disease, or vaccine escape - increased transmissibility alone is enough to cause severe problems.

Right now, Scotland is recording around 3000 cases per day and roughly 2-4% are ending up in hospital.

READ MORE: Glasgow's Delta variant outbreak is warning against 'traffic light' travel

Even if nothing else changed, simply being able to reach and infect more people would ratchet up the pressure on the NHS over winter.

Already, boosters have been turning the tide on Covid hospital numbers in Scotland, especially among the over-70s whose admissions have been cut by 51% in the four weeks to November 16 - much faster than any other age group.

HeraldScotland: Boosters have been rapidly driving down Covid cases among the over 60s (above) and hospitalisations in the over-70s (below), but in the UK Delta currently accounts for around 99% of casesBoosters have been rapidly driving down Covid cases among the over 60s (above) and hospitalisations in the over-70s (below), but in the UK Delta currently accounts for around 99% of cases

HeraldScotland:

But Omicron's mutations appear to mirror many of those seen in the Beta variant, which signals potential trouble ahead.

Beta - first detected in South Africa - is the most vaccine-resistant variant to date, but never posed a major danger because it proved less transmissible than Delta.

Even soon after a second dose of the Moderna vaccine - which appears to be the most effective against it - protection against symptomatic infection was just 60%. With Pfizer it was 50-60% and AstraZeneca 40-50%.

Damage control in the short-term would still rely on maximising vaccine coverage - perhaps accelerating boosters into younger age groups, doing everything possible to vaccinate the unvaccinated, and perhaps even expediting the rollout of jags to five to 11-year-olds.

But there is little doubt that a variant which was simultaneously much more transmissible and around a third more vaccine resistant than Delta, would be catastrophic for the NHS.

And that is before we even contemplate whether it is more virulent (something we never really faced with Delta).

READ MORE: What's really behind the worst winter crisis facing Scotland's NHS?

It is difficult to see how we could avoid another lockdown - even just a circuit-breaker type - in a bid to control and contain such a variant, given the severe strain already on the health service.

Too many patients have already seen "non-urgent" treatment - and even some cancer operations - delayed by Covid.

Hospital beds are running out due to staff shortages and social care bottlenecks. NHS staff are beyond exhausted.

A serious Covid wave on top would tip the NHS from breaking point to broken, with the very real risk that care would have to be rationed.

HeraldScotland: Border controls may need to be tightened further in the days and weeks ahead, especially as the festive season approachesBorder controls may need to be tightened further in the days and weeks ahead, especially as the festive season approaches

All is not necessarily lost, however.

One positive is that the UK Government has at least learned some lessons from Delta and reacted swiftly, banning flights from southern Africa and imposing hotel quarantine.

On the downside, the variant has already spread to Belgium and Hong Kong at least, so it might be wiser to quarantine and screen all arrivals.

Secondly, Pfizer and Moderna have already been working on Beta-tailored vaccines, and could - quite quickly - tweak them to target Omicron, though clinical trials would still be required.

Finally, it could still turn out to be less toxic than it currently looks.

Maybe it will be more transmissible but substantially less virulent, morphing into a milder disease.

Or maybe it won't outcompete Delta afterall, or be less vaccine-resistant than its mutations suggest.

For now, we should hope for the best - but hope our governments are prepared to act early to avert the worst.