Fears over the ‘kraken’ variant of Covid may be overblown, experts warned today as data showed it is not spreading as quickly as first feared.
XBB.1.5 – a spin-off from Omicron – is said to be the most transferrable strain yet.
Its emergence fueled concerns it would break through vaccine-induced immunity after triggering a “staggering spike” in cases in the US, where it was first discovered.
But the Centers for Disease Control and Prevention (CDC), the US agency responsible for fighting the virus, has now downgraded its estimates of how many infections the variant causes.
XBB.1.5 – a spin-off from Omicron – is said to be the most transferrable strain yet. But the Centers for Disease Control and Prevention (CDC), the American agency responsible for fighting the virus, has now downgraded its estimates of how many infections the variant causes (from 41 percent to 18 percent a week). December 31
Latest data shows that XBB.1.5 accounted for only 18.3 percent of US Covid cases in the week ended December 31 (second right column, dark blue).
Previously, 41 percent of infections in the week were reported as XBB.1.5 (rightmost column, dark blue)
Latest data shows the variant accounted for just 18.3 percent of cases in the week ended December 31.
Previously, an estimated 41 percent of infections in the week were caused by XBB.1.5.
Professor Paul Hunter, a public health expert at the University of East Anglia, told Web: “The CDC estimate of the growth rate of XBB.1.5 appears to be overestimated.
“They downgraded their estimate of the percentage of all infections due for the week ending December 31 from 40.5 percent to just 18.3 percent in the same week.”
Professor Hunter admitted it was “still growing” but insisted the situation was “much less scary than it seemed a few days ago”.
Despite the overestimate, the latest CDC numbers show that XBB.1.5 infections now account for a larger proportion of all cases.
About 27.6 percent of the Covid cases sequenced in the week ended January 7 were caused by the variant.
It remains the only subvariant with increasing prevalence in the US.
But as in the UK, the data reflect only a fraction of the cases actually observed.
Professor Hunter said: “Certainly the very, very rapid growth that was suggested last week does not appear to be the case.
“The growth rate of an infection is largely a reasonable indicator of the eventual height of the curve (the peak number of infections). So very rapid growth early on leads to many more infections at its peak.
“But if you look at more recent data, the growth rate in the US seems to be slowing down quite a bit.
“But sequencing results in recent weeks are often quite uncertain, as it can take up to three weeks for positive results to be sequenced. Monitoring systems during holiday periods are also particularly unstable.”
He added: “So as of this writing, it doesn’t look like XBB.1.5 will cause a huge problem like many thought last week.
“But wait another week until the holiday season is a good two weeks over and we can have more confidence in the surveillance data again.”
Cases are estimated to have doubled in December, just as the XBB.1.5 “Kraken” variant began sweeping the UK. Analysts say nearly three million people had the virus during the festival week
Figures from the Sanger Institute, one of the UK’s largest Covid surveillance centres, show that 4 per cent of cases in the week to December 17 were caused by XBB.1.5 (shown in purple, lower right corner).
The graph shows the weekly hospital admissions per 100,000 people for Covid (red) and flu (blue). Surveillance figures from the UK Health Security Agency showed Covid admissions fell from 12 to 11 per 100,000 people, while admissions fell to 8 per 100,000 in the week ending January 1
NHS data shows an average of 995 Covid patients were admitted to hospitals across England in the week to January 2. The figures suggest the number of people seeking NHS care because of the virus peaked on average just before Christmas and has been trending downwards since
On December 17th, XBB.1.5 was listed for the first time in the institute’s virus dashboard, which is updated weekly
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XBB.1.5 has received mutations, including F486P, that help it evade Covid-fighting antibodies generated in response to vaccination or a previous infection.
Another change – S486P – is said to improve its ability to bind to cells.
Figures from the Sanger Institute, one of the UK’s largest Covid surveillance centres, show that 4 per cent of cases in the week to December 17 – the latest date for which data are available – were caused by XBB.1.5.
It is the first time the strain has been included in the institute’s virus dashboard, which is updated weekly.
The strain is a mutated version of Omicron XBB, which was first recorded in India in August.
XBB, a merger of variants BJ.1 and BA.2.75, led to a quadrupling of cases in some countries in just one month.
Latest figures from the UK suggest one in 20 people contracted Covid over the Christmas holidays.
Cases are estimated to have doubled in December, just as XBB.1.5 began sweeping the UK.
Analysts say nearly three million people had the virus during the festival week, reflecting the level of the summer, when experts wanted the return of pandemic-era restrictions like masks.
Experts fear the strain, believed to be the most communicable yet, will accelerate the winter wave in Britain and put even more pressure on the ailing NHS in the coming weeks.
The ailing healthcare system is already being hit by its worst flu outbreak in a decade. The winter pressures have sparked fresh calls for a return of measures to protect the NHS.
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