New Crown XBB mutant strain is here, stay tuned but no need to fear

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On December 31, 2022, the latest data released by the CDC showed that XBB.1.5 accounted for 41% of new crown cases in the U.S. and has replaced BQ.1.1 and BQ.1 as the dominant strain as the number one prevalent strain in the U.S.

Both XBB.1 and XBB.1.5 are subbranches of XBB. The Omicron XBB mutant strain first appeared in India in August 2022 and spread rapidly thereafter, soon becoming a major endemic strain in Singapore and Malaysia. Since then, XBB mutants have evolved into subbranches of Omicron, including XBB.1 and XBB.1.5.

The pathogenicity of XBB has not increased significantly

Now, XBB has also emerged in China.

Xu Wenbo, director of the Institute of Viral Diseases of the Chinese CDC, introduced that China has monitored the introduction of BF.7, BQ.1, and XBB into China in the past three months, with a total of more than 130 subbranches of Omicron imported into China, with BQ.1 and its subbranches detected in 49 cases in 9 provinces and XBB subbranches detected in 11 cases in 3 provinces.

With the emergence of XBB and its subbranches XBB.1 and XBB.1.5 globally and in our country, some sources claim that these mutant strains mainly attack the cardiovascular and digestive systems and tend to cause diarrhea. Therefore, there is now a wave of drug rush in some places, with enteritis tablets, montelukast, norfloxacin capsules, and lactobacillin tablets off the market.

There is no excuse for purchasing medication. However, other situations need to be considered as well. One, whether XBB and its sub-branches can cause cardiovascular and gastrointestinal symptoms, there is no definite clinical evidence; two, even if you want to use drugs, you need to use them under the guidance of a doctor, do not use them yourself.

The key issue is that XBB and its sub-branches need to be clarified as to where the epidemic is going now and how much damage it can do to people.

As far as the current situation is concerned, XBB has only increased immune escape, but the symptoms caused are not serious and the lethality rate is not high, so there is no need to be overly worried about XBB and its subbranches.

According to the results of sequencing of virus strains extracted from infected patients in China, the domestic infection is still dominated by subtypes BA.5.2 and BF.7 of Omicron, and it remains to be seen whether a source of infection dominated by XBB and its subbranches will be formed in the future. But even so, it is unlikely that XBB and its subbranches will raise a bigger storm than the one created by BA.5.2 and BF.7.

Based on the current clinical situation in other countries, such as the United States, the pathogenicity of XBB and its sub-branches has not increased significantly, and the symptoms people experience after infection are similar to or even less severe than those caused by other subtypes of Omicron, and there is no increase in mortality. The first time I saw this, I was able to see that the virus is a normal variant of Omicron.

▲On Dec. 27, people buy medicine at a pharmacy in Tianjin.

It is still necessary to be alert to the infectiousness of XBB

It is still important to note that there is a particular variant of XBB. Related studies have shown that XBB.1.5 differs from its sibling strains in that it has an additional key mutation, F486P, that has a stronger affinity for the human angiotensin-converting enzyme 2 (ACE2) receptor, which is the gateway for the virus to enter human cells, making it easier for the XBB.1.5 variant to invade human cells.

A consequence of this is that XBB.1.5 has a higher immune escape capacity. This means that even with vaccination, whether inactivated or mRNA, immune protection against this variant may be reduced, i.e. XBB.1.5 is more likely to cause infection than other strains.

Meanwhile, natural infection with the virus is equivalent to a vaccination that produces neutralizing antibodies in the body, but because of the enhanced immune escape of XBB.1.5, the immunity acquired after natural infection may likewise be reduced, making it difficult to block XBB.1.5 infection. However, small molecule antiviral drugs are equally effective against XBB.1.5.

These conditions can also be explained by the mutation of the virus. Even XBB and its sub-branches are derived from mutated strains of Omicron.

To date, there are only five strains of concern announced by the WHO, namely Alpha, Beta, Gamma, Delta, and Omicron variants. The World Health Organization only upgraded the Omicron variant to the currently prevalent variant of concern on November 26, 2021.

Currently, the Omicron variant is still mutating, and WHO observations indicate that there are at least hundreds of other subbranches of Omicron mutating. xBB is only a minor branch of Omicron, and the evidence observed so far is that it is not very pathogenic or lethal, but only has an increased immune escape capacity.

In this case, it is the secondary infection that needs to be guarded against, especially since XBB.1.5 may trigger secondary infection. However, the majority of available secondary infections (not necessarily caused by XBB.1.5) indicate that their symptoms are less severe than the first.

The best way to avoid secondary infections and infections caused by XBB.1.5 is to get a booster vaccination. Of course, you don’t need to get the vaccine just after the infection, but you can wait 4-6 months before getting the second booster. It is also important to take care of yourself before and after the Chinese New Year by wearing a mask and washing your hands regularly.

It is also important to note that if you have a fever that does not subside, breathing difficulties, severe nausea, vomiting, diarrhea and other digestive symptoms, poor mental status, or aggravation of an existing underlying illness, you should seek medical attention.

We have been through a big storm, and on the basis of good protection and preparation, there is no need to worry excessively.