Should I be concerned about XE, the new COVID hybrid

(ORDO NEWS) — A new hybrid variant of COVID-19, dubbed XE, has recently raised new concerns.

The XE is a combination of the highly transmissive BA.1 and BA.2 Omicron variants and was first spotted in the UK in mid-January. Its spike protein is derived from BA.2, which is potentially good news for New Zealand as this variant is dominant (over 90 percent of recent infections) and people who have been infected should have some protection against XE.

To date, about 700 viral genomes have received XE status worldwide. This variant has been found primarily in the UK, and now in a few cases in other countries, including Thailand and the US, most likely due to travel-related spread of the virus.

According to current estimates from the UK, the XE has a slight (5-10 percent) transmission advantage over the BA.2, making it the most transmissible Omicron sub-variant identified to date. Every time a new, more transmissible variant appears, it has a chance to become dominant over time.

XE has not yet received its own Greek letter. For now, it belongs to Omicron until significant differences in virus transmission and disease characteristics, including severity, are identified.

So far, there is not enough data to draw firm conclusions about the transmissibility of XE, and there is almost no data on the severity of the disease or the ability to evade immunity.

How do hybrid options arise?

Usually, each individual virus is almost an exact copy of its single parent virus. But viruses also undergo a process called recombination – they can have two parents.

Recombinant viruses can occur when two or more variants infect the same human cell, allowing the variants to interact during replication. This can lead to mixing of their genetic material, forming new combinations of viruses.

Some viruses, such as influenza, have segmented genomes and can mix entire segments together in a process called reassortment. Viral recombination and reassortment are common among viruses, but their rate varies greatly depending on the type of virus and the likelihood of coinfection.

More than two years after the onset of the pandemic, and with high levels of infection worldwide, recombination of the SARS-CoV-2 virus is more likely and easier to detect than at earlier stages.

The global wave of Omicrons has led to a rapid increase in the prevalence of COVID, which increases the likelihood of coinfection and gives the virus a better chance of recombination.

We also have more ability to detect recombination than before. At the beginning of the pandemic, there was little genetic diversity in the SARS-CoV-2 virus, and recombinants were similar to non-recombinants because the two parental viruses were nearly identical.

But now there are several genomically distinct variants infecting people in the same locality, making recombinant genomes much easier to spot among the millions of genomes created to date. Viral recombination is likely to play an important role in the ongoing evolution of SARS-CoV-2.

Known viral recombinants

Recently, several recombinant variants of SARS-CoV-2 have been identified, named XA, XB, XC, etc., up to XS. Some of these variants were sequenced as early as mid-2020. Some of them have met only a few times, while others have been assigned several hundred genomes.

Currently, two main types of recombinants are often found: mixtures of Delta and Omicron (dubbed Deltacron) and mixtures of Omicron subvariants.

Some of these recombinants are closely monitored. These include XD and XF, which are composed of Delta genetic material and the BA.1 Omicron subvariant.

XD was first discovered in France and contains a mixture of a spike protein from BA.1 and the rest of the genome from Delta. There was some concern that it would inherit BA.1’s ability to bypass our immune defenses and Delta’s high virulence. To date, XD does not seem to be spreading widely or rapidly.

Should we be worried?

So far, there is no evidence that recombinant viruses pose a greater threat to public health than any other options. But recombinants should be closely monitored to see if they cause changes in virus transmission, disease severity, or the ability to evade vaccine-induced immune defenses.

For now, there is no need to worry too much about XE. But we need to continue to monitor SARS-CoV-2 globally to identify new variants and understand what risk they might pose.

Our best approach to limiting the rate of emergence of new recombinants or other variants is to limit the spread of the virus. Despite widespread worldwide recognition that SARS-CoV-2 will be with us for the foreseeable future, we can still use protective measures to slow down and suppress the virus.

These include regular testing, isolation in case of infection, wearing quality masks and improved ventilation. All these measures reduce the chances of getting a coinfection and becoming a carrier of a new recombinant. Conversation


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