The biggest concern of COVID-19 is the constant evolution of the virus.
On 11 April, the World Health Organization announced that two new subvariants of the Omicron strain, BA. 4 and BA. 5, had been placed on the surveillance list because both subvariants had “additional mutations” that required further evaluation of whether they were more infectious, pathogenic and had an impact on immune escape.
The Novel Coronavirus has been evolving since its discovery, but only a few of the new coronavirus variants have serious implications: they enhance transmission, evade immunity from vaccination or infection, and cause more severe disease.
Ba. 4 and BA. 5 have been widely distributed
The daughter variant ba. 2 of the omicron variant is the dominant strain in the world, accounting for 94% of sequenced cases. It has been shown to be more transmissible and evade immune protection than other variants, but the evidence so far does not prove that it causes more severe disease.
Samples of BA. 4 and BA. 5 originally came from South Africa, According to Reuters. As of last week, all the cases of BA. 5 were in South Africa. But on 11 April Botswana said it had found cases of BA. 4 and Ba. 5. All infected people were between the ages of 30 and 50, all had been vaccinated and had mild symptoms. This means that ba. 4 and BA. 5 appear to evade existing immune protection and that the infected population is not elderly or infirm, but middle-aged and middle-aged people are equally likely to be affected.
Subsequently, cases of BA. 4 and BA. 5 were reported in Denmark, Germany, and the United Kingdom. Only a few dozen cases have been reported by GISAID, a public database on global epidemics. Although not many in number, in terms of geographical distribution, the distribution is quite extensive.
These two subvariants have been listed as Variant of Interest (VOI) by the UK Health Safety Agency (UHSA). According to the UHSA, BA. 4 has all the mutations or deletions of the BA. 2 lineage.
XE recombinant viruses are also spreading faster
In addition to the emergence of a new variant of omicron, the XE recombinant virus, which was just discovered some time ago, also seems to be “accelerating” the spread.
More than 600 gene sequences have been reported and identified from a previously re-engineered strain known as XE found in the UK, according to a report published on March 30 by the World Health Organization. Early investigations suggest that the new strain has a growth rate advantage of about 10% over the currently dominant omicron BA. 2 strain, but it remains to be seen whether it will be a potential threat in the future due to the small data sample.
The report identified the recombinant strain as a recombination of the ormica strains BA. 1 and BA. 2, which it named XE. XE was first discovered in Britain on January 19 this year. The UK Health and Safety Agency’s (UKHSA) announcement on 25 March confirmed that 637 cases of XE infection had been confirmed in the UK at that time. But by April 5, the number had risen to 1, 179. The UK Health Department revealed that XE has increased by more than 20. 9% in the past three weeks.
Not only the United Kingdom, but Japan also announced on The 11th, that a woman who entered the country also confirmed XE infection. This is the first time the strain has been detected in Japan. Canada’s health agency also announced last week that six cases of XE infection had been reported in Canada.
With the emergence of BA. 4/BA. 5 at a time when XE is spreading around the world, it is worth paying closer attention to what characteristics these new strains have and whether they will change the trajectory of the global epidemic.