Highly immune evasive Covid variant rapidly becoming dominant in U.S.

Covid surge in China

China has maintained a strict zero-Covid policy since the beginning of the outbreak, closing down cities and towns with populations of millions of people due to a few coronavirus cases. However, in early December, the zero-Covid policy, which had been in place for several years, was lifted, and the virus began to spread rapidly across the country.

At the same time, official epidemiological statistics have been abandoned, leaving only estimates of the scale of the problem in the world's most populous country. Several European countries have closed their borders to China, and some experts have warned that the Chinese outbreak could create a new mutation of SARS-CoV-2 that could devastate the world. But despite this, the world's epidemiologists are now turning their attention from China to the United States, where a new variant of concern is in the spotlight.

XBB 1.5 – Cab this be a "super variant"?

The variant is XBB.1.5, dubbed "nightmare" variant, is a highly contagious "recombinant" variant that spawned from two different BA.2 variants, BA.2.10.1 and BA.2.75.  It is related to the XBB variant, which was previously behind a Covid surge in Singapore, India and also in the United States.

Andrew Pekosz, a virologist at Johns Hopkins University, told CNBC the XBB.1.5 has an additional mutation that makes it bind better to cells.

"The virus needs to bind tightly to cells to be more efficient at getting in and that could help the virus be a little bit more efficient at infecting people," Pekosz said.

Professor Paul Hunter, an epidemiologist at the University of East Anglia, told MailOnline that the majority of new variants 'fizzle out in a few weeks'.

However, the sharp increase in XBB.1.5's prevalence is

certainly very worrying' and suggests 'a pretty dramatic growth advantage and enough to drive a new wave of infections,

he said.

But he noted that the US data is based on estimates and it is difficult to accurately measure Covid data, including variant levels, due to delays in testing and reporting.

Professor Hunter said this makes it 'too early to say whether XBB.1.5 will cause big problems' or not, though it will likely become the dominant variant in the UK. Covid hospitalisations are already rising in the U.S.

Where is XBB.1.5 spreading?

As in the case of most new variants, it is unclear where XBB.1.5 is coming from, but it is certainly in the U.S. and spreading fast.

Within the last two months, tracking numbers from the Centers for Disease Control and Prevention (CDC) showed the XBB.1.5 variant has climbed to now make up more than 40% of cases in the U.S., nearly doubling in prevalence over the past week. In the Midwest, however, the numbers are much lower, with XBB.1.5 making up just 6% of cases.

The emergence of XBB.1.5 in the United Kingdom has been reported recently. Figures from the Sanger Institute, one of the UK's largest Covid surveillance centres, shows 4% of cases in the week to 17 December were caused by XBB.1.5. It is the first time the strain has been listed on the institute's virus dashboard, which is updated weekly.

What do experts say?

Although many public health experts are expressing concern about the rising COVID cases in China, infectious disease experts have been increasingly worried about the XBB.1.5 variant.

Ironically, probably the worst variant that the world is facing right now is actually XBB,

said Dr. Michael Osterholm, an infectious disease expert at the University of Minnesota, in a recent interview with Reuters.

Osterholm added that seven of the 10 U.S. states where cases and hospitalizations are rising are in the Northeast, concurrent with an increase of XBB cases there, he said.

Every previous two winters, we have seen a surge of infections that peaked in mid January... and I expect the same to happen this year,

said John Moore, a professor of microbiology and immunology at Weill Cornell Medical College in New York.

He added that the difference between last two years and this year is that there has not been a significant increase in the death rates.

There’s no indication XBB.1.5 causes more severe illness than any other omicron virus, Dr. Barbara Mahon, director of CDC’s Coronavirus and Other Respiratory Viruses Division, told NBC News. 

While overall Covid hospitalizations are rising around the country, areas such as the Northeast that have seen high levels of the new variant have not experienced a disproportionate increase in hospitalizations, Mahon said.

“We’re seeing hospitalizations have been notching up overall across the country,” she said. “They don’t appear to be notching up more in the areas that have more XBB.1.5.”

Epidemiologist Eric Feigl-Ding called XBB.1.5 a 'super variant' on Twitter, warning that it has shown great ability to evade antibodies. He presented an animation showing the rapid spread of the new variant.

Global spread in just daysLets be clearthe super variant is a US-origin variant from Northeast US. The is cowardly in refusing to admit it. Watch the incredibly fast spread (animation by ). needs to wake up. #XBB15

— Eric (Feigl-Ding) January 3, 2023

Yunlong Richard Cao, Assistant Professor at Peking University (Biochemistry & Immunology, Host Immune Response, Antibody Drug & Vaccine Design), tweeted last week that XBB.1.5 is equally immune evasive as XBB.1, while it has a much higher binding affinity to SARS-CoV receptor (humanangiotensin-converting enzyme 2 [hACE2]).

The superior growth advantage of XBB.1.5 has been well-documented by many colleagues . Here I'll add some experimental data:1) XBB.1.5 is equally immune evasive as XBB.1, but2) XBB.1.5 has a much higher hACE2 binding affinity. 1/ @JPWeiland

— Yunlong (Richard) December 28, 2022

What is there to know about the previous "nightmare" variant?

Referred to as the "nightmare" variant in some reports at the end of October 2022, XBB is the combination of two omicron subvariants - BA.2.10.1 and BA.2.10.75 - and is said to have a "significant growth advantage," said Dr. Maria Van Kerkhove, an infectious disease specialist and the technical lead for COVID-19 response at the World Health Organization, NBC Chicago reported.

Van Kerkhove explained data about the latest strain remains limited, but said the one study that was conducted with XBB shows "significant immune invasion."

We do know this recombinant has a significant growth advantage. All of the subvariants of omicron are showing increased transmissibility and properties of immune escape,

Van Kerkhove said.

"With this XBB recombinant we have one study based on a pseudo virus, so not a live virus, that is analyzing antibody escape and it's showing significant immune evasion. And this is of concern for us because we need to ensure that the vaccines that are in use worldwide will remain effective at preventing severe disease and death," she added.

Hungarian virologist Gábor Kemenesi wrote at the end of October that a significant change in the coronavirus landscape was the now visible emergence and spread of recombinant variants of the virus. This simply means that different variants are mixing at the gene level and are also evolving towards the aforementioned properties (avoiding immunity, better spread, etc.). He says we have reached the stage in the pandemic where several variants are spreading in parallel around the world and mutating in very similar directions (what researchers call convergent evolution).

"This broadly suggests that the virus is having very similar effects everywhere, probably due to the fact that most of the world already has some form of acquired immunity - either vaccinated, or encountered the virus, or both. Several variants of the virus, which have emerged and are spreading in parallel, are trying to trick the immunity they have developed by picking up similar mutations, at least at the antibody level - in effect making it easier to 'catch it again'," he explained.

Thanks to the addition of a third booster vaccine, the coronavirus, which is spreading explosively in China, is less dangerous for Europeans, Gábor Kemenesi, assistant professor at the Faculty of Natural Sciences of the University of Pécs told Infostart.

Addressing XBB.1.5, he said this was to be expected and there have certainly been similar versions of the virus before, but this one is interesting in that it is gaining ground. "But what we are used to with this virus is that every year or two a new variant appears that for some reason is able to spread more than the previous ones," said the assistant professor, adding that there is no evidence yet that it is more serious, let alone able to evade the vaccine.

Cover photo: Getty Images