There is no more "72- variation" strain of the new coronavirus than Aomi Kerong.
As you can see from the name, BA.1, BA.2, BA.2.12.1... There are also BA.1 and BA.2 composed of XE, and recently there have been BA.4 and BA.5 in the United States and other places.
With the continuous mutation of Aumechjong, some countries seem to have ushered in a new wave of epidemics.
So, how many variants of Ami kerong there are? How has it affected the pandemic?
The main 5 subtype variants
Since being tested in November 2021, Omilon has evolved at least five major subtypes, namely BA.1, BA.2, BA.3, BA.4, and BA.5. Among them, the BA.2 subtype strain is currently the highest proportion and the most prevalent in the world.
According to a WHO survey in mid-April, of the more than 400,000 new coronavirus genome sequences it collected, 99.8 percent of them were BA.2 variants. The proportion of BA.1 and BA.3 subtypes is relatively small, less than 0.1%.
BA.4 and BA.5 were detected in South Africa in January and February of this year, respectively, and are the Omiljung mutant strains with a new combination of mutations. They share mutations with BA.1 and BA.2 and are most similar to BA.2.
On 11 April, the World Health Organization (WHO) added the BA.4 and BA.5 variants to a surveillance list. According to incomplete statistics, these two strains have appeared in 21 countries around the world.
In addition to the above five subtypes, BA.2 is also evolving, evolving new strains such as BA.2.12.1 and BA.2.3.
BA.2.12.1 was first detected in the UK on March 23, and since then there have been confirmed cases in eight countries, including Australia, Israel, Singapore, Denmark, Austria, and South Korea. Among them, BA.2.12.1 has the strongest upward momentum in the United States.
On April 25, 16 patients infected with the evolutionary branch of Omi Kerong BA.2.3 were found in Yantai, Shandong Province. This evolutionary branch has also appeared in Thailand, Italy, Canada and the United States, but it is relatively small and is not easy to become a dominant strain.
In addition, Omexon has recombined to produce new strains, including XE, XD and XF.
XE is the result of the restructuring of the Omirkjong BA.1 and BA.2, which was first detected in the UK on 19 January 2022. According to the latest data from the UK Safety and Health Agency, as of April 5, 1179 people in the UK have been infected with the XE variant, and the cases are mainly concentrated in densely populated London and the east of England.
XD and XF are the result of the reorganization of Delta and Omexon BA.1, hence the name "Deltacroon". XF is the result of the restructuring of the British BA.1 and Delta, and the XD is the result of the French BA.1 and Delta reorganization.
Some strains have increased transmission
In the process of evolution, the spread power of Omikeron is also constantly improving. Among them, BA.2.12.1 is the most obvious.
BA.2.12.1 is currently spreading rapidly in the United States. According to the latest data from the U.S. Centers for Disease Control and Prevention (CDC), while the main epidemic strain in the United States is still BA.2, the proportion of infections caused by BA.2.12.1 is also rising rapidly. As of April 30, BA.2.12.1 accounted for 36.5% of the United States, compared with only 0.5% on March 12.
In terms of the rate of case climbing, the spread of BA.2.12.1 is comparable to THAT of BA.2. Both reached about 40% of cases in a 7-week period. According to CDC's forecasts, BA.2.12.1 appears to spread faster, 23%-27% more than BA.2.
The U.S. Department of Health divides the U.S. into 10 regions and counts the proportion of strains in each region. Among them, New York, New Jersey, Puerto Rico and the Virgin Islands are currently the highest proportion of BA.2.12.1 variants. As of 30 April, 61.93% of the infections in the region accounted for BA.2.12.1, compared with 37.61% of BA.2.
The rapid spread of BA.2.12.1 has led to a resurgence in the number of confirmed cases in New York. In early March, New York's risk level remained low, with a single-day low of 296 new cases (12 March). Affected by BA.2.12.1, the city's new daily confirmed cases began to rise gradually after March 21, and peaked on April 25 (3316 people).
This has also led to an increase in the number of hospitalizations. Hospitalizations in New York City rose in March and April, with 81 hospitalized for COVID-19 on April 22, a peak in March and April.
However, compared with the previous round of the epidemic, the number of hospitalizations is still at a low level. The last outbreak peaked on 2 January, when 1,316 hospitalizations were made, 16 times more than the current number of hospitalizations, and the number of hospitalizations in early May showed a downward trend.
Judging by the current number of deaths, BA.2.12.1 has not had much impact. The number of deaths in New York City remains volatile and downward, with no more than 10 deaths per day in April, compared with a previous peak of 131 on January 11.
In the recombinant variant, XE propagates faster.
The UK Safety and Health Agency calculated the sampling data from January 15 to March 30 through statistical models, compared the probabilities of XE in genes and BA.2 in the control group, and found that the median weekly growth rate of recombinant strain XE was 12.6% higher than THAT of BA.2, and its growth rate was as high as 20.9% in the last three weeks.
The two recombinant variants of XD and XF do not propagate as fast as XE.
Compared to XE, XD contains Delta's structural protein, which inherits more of Delta's properties and spreads relatively slowly. By 7 April, a total of 49 cases of XD had been reported in the global database, most of them in France.
Most of the sequences of XF are similar to BA.1, and the rate of infection of BA.1 is lower than that of BA.2, so the rate of infection of XF does not exceed BA.2. There are currently 38 confirmed XF cases in the UK, the earliest sample was on 19 January, and no cases have been found since mid-February. Therefore, XD and XF are not widely disseminated.
Immune escape is present
Although no relevant studies have shown that these new strains are more toxic, three strains, including BA.4, BA.5 and BA.2.12.1, have immune evasion characteristics, which may lead to a decrease in the effectiveness of the vaccine.
Tulio de Oliveira, a professor of bioinformatics at Stellenbosch University in South Africa, said that because BA.4 and BA.5 mutate in the spectrum that allows the virus to evade immunity, it means that in part, they are able to evade antibody systems that have been infected with Omicron or vaccinated.
According to Tulio de Oliveira, more than 90% of south Africa's population currently has some degree of immune protection, but from the data point of view, the recent confirmed cases in South Africa have increased again, and are entering the fifth wave of the epidemic.
In early April, south Africa's fourth round of the outbreak has leveled off, with around 20 new cases per million people in a single day, down from its peak of 390 new cases per million people in a single day.
But from mid-April, the number of new cases in a single day in South Africa climbed again. On 3 May, South Africa saw 76 new cases per 100 million people, five times as many as on 2 April (15 new cases per 100 people).
As of April 29, BA.4 accounted for more than 35% of all provinces in South Africa, while as of April 22, BA.5 was detected in 6 places, including Gautengau, Limpopo province and Mpumalanga province in South Africa, accounting for about 20%.
According to the latest research from the African Institute of Health Research, for people who have been infected with Omilon BA.1 and have not been vaccinated, when exposed to BA.4 and BA.5, their serum antibodies have decreased by more than one-seventh compared with normal levels, and for those who have been vaccinated, the degree of antibody decline in the body has also reached one-third.
According to the latest research from Peking University, the effectiveness of vaccines against BA.4, BA.5 and BA.2.12.1 has also declined. The study found that even after three doses of the vaccine, compared with BA.1, the level of neutralizing antibodies in the human body decreased by 3.7 times in the face of BA.2.12.1, and the level of neutralizing antibodies decreased by as much as 8 times in the face of BA.4 and BA.5.
In addition, for the toxicity judgment of the XE recombinant strain, Susan Hopkins, chief medical adviser of the UK Health Agency, said that it was not clear and there was not enough evidence to prove its severity. According to its structure, its spike proteins are all derived from the sub-variant BA.2, so its disease severity should also be similar to BA.2.
From the current data, these emerging mutant strains have shown strong contagiousness and have not yet caused a large impact. However, due to the certain lag in the death situation and severe illness, it cannot be taken lightly.
As to whether the direction of virus mutation must be "sustained diminishing toxicity", virologist Wendy M. Lee at Imperial College London said: Barkley said no in the interview, arguing that the virus will evolve rapidly through recombination, which is likely to produce new strains that both immune escape and cause more serious disease.
Therefore, although the number of cases of COVID-19 infections worldwide continues to decline, the outbreak has not reached the end of the announcement. The WHO also calls on all countries to continue to monitor COVID-19:
"The virus will not disappear because countries stop tracking. It is still spreading, it is still changing, it is still taking people's lives. ”
Column editors-in-chief: Zhang Mo, You Shujie
Source: Author: Lian Junxiang Tong Ruonan