World Health Organization

Omicron XE Variant: What We Know About the Hybrid COVID Variant

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The hybrid omicron XE strain, also named the "Frankenstein" variant, has spreading across the globe, but should people in Illinois and Chicago be worried?

Here's a look at what we know so far:

What is XE?

The XE variant is a recombinant, meaning it has parts of two different variants rearranged into a new virus, which in this case are BA.1, the original strain of omicron, and BA.2, known as "stealth omicron."

Recombinant variants themselves are not out of the ordinary, according to health officials.

"Recombinant variants are not an unusual occurrence, particularly when there are several variants in circulation, and several have been identified over the course of the pandemic to date," Hopkins said. "As with other kinds of variant, most will die off relatively quickly."

According to the Centers for Disease Control and Prevention's website, XE isn't currently being monitored by U.S. epidemiologists nor has it been labeled as a "variant of interest" or "variant of concern."

WHO said it will continue to study recombinants and provide updates as further evidence becomes available.

Is XE in Chicago or Illinois?

So far, no cases of the XE variant have surfaced in Chicago or Illinois, according to health officials.

In the week of April 3-9, all COVID cases in Chicago were identified as the omicron strain, with about 86% of cases reported as BA.2. Nevertheless, no XE cases have been reported thus far, based on data from CDPH.

In all of Illinois, 99% of COVID cases were of the omicron variant in the week of April 3-9, according to data from the Illinois Department of Public Health, with less than 1% of cases being delta. No cases have been reported at XE.

An earlier email from CDPH said it continues to closely monitor circulating variants, and is part of regional and national surveillance efforts.

Chicago Department of Public Health Commissioner Dr. Allison Arwady has said she's not concerned about the new strain just yet.

"Whenever you see a new variant emerge, the main thing is it's got... it may have some little advantage, maybe a little more contagious, but no, this is not one at this point that I have any specific concern about," she said. "It remains sort of a version of omicron."

How contagious is XE?

XE might be the fastest-spreading strain yet, according to preliminary research, but studies are underway to determine the exact contagiousness of the variant.

Data has shown that XE has a growth rate of 9.8% above BA.2, the UK Health Security Agency revealed in late March.

The World Health Organization has released similar information, citing estimates that show XE is 10% more transmissible than BA.2. However, those findings require further confirmation, the agency noted.

The more contagious omicron subvariant BA.2 has become the dominant COVID-19 strain in the U.S., but international health experts are putting an increased focus on a new hybrid variant that may even be more infectious.

BA.2 was previously identified as the most transmissible variant as it spreads about 75% faster than BA.1, according to health officials.

"Any time there is a more transmissible virus, it has the chance of becoming the predominant virus across the world," said Hannah Barbian, a genomic epidemiologist at the Regional Innovative Public Health Lab at Rush University Medical Center.

Experts said COVID vaccines have been effective against all variants that have surfaced, when it comes to preventing hospitalizations and death. More studies, however, are needed to see what impact vaccines could have on the XE variant.

Why is XE called the 'Frankenstein' variant?

Because the variant combines both BA.1 and BA.2 to create XE, some health experts say the two viruses combine in a "Frankenstien"-style with a single host.

However, one Chicago expert said recombinant variants, such as the XE strain, are fairly common and the name "Frankenstein" could be misleading.

"Recombinants happen naturally with viruses quite often, actually," said Hannah Barbian, a genomic epidemiologist at the Regional Innovative Public Health Lab at Rush University Medical Center. "So I think Frankenstein is maybe a little misleading in that it suggests some kind of, you know, like, manmade type of origin, but recombinant viruses are just a natural process in viral biology."

What's happening in the UK and across the globe?

XE was first detected in mid-January in the United Kingdom, where more than 600 cases have been reported since, according to the UK's Health Security Agency.

As of April 5, 1,125 cases of XE had been identified in the U.K., up from 637 on March 25. The earliest confirmed case has a specimen date of Jan. 19 of this year, suggesting it could have been in circulation in the population for several months.

According to data from the health agency, cases of the new strain have almost doubled in Britain since first detected.

As of Tuesday, Japan has reported its first case of omicron XE in a woman in her 30s who arrived at Narita International Airport from the U.S. on March 26. The woman, whose nationality was not immediately disclosed, was asymptomatic, Japan's health ministry said Monday.

XE has since been detected in ThailandIndia and Israel. It is suspected that the latter Israeli cases may have developed independently. The U.S. has not yet reported any XE cases.

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