Omicron “virulence” is not low, Delta may make a comeback!

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It is generally believed that the new coronavirus Omicron strain is more contagious than other variants, but the severity of disease is less. But a large U.S. study published on the preprint platform “Research Square” on May 2 said that Omicron’s “virulence” is not low, but is similar to what was previously thought. Just as serious as the previous variant.

The influence of Omicron is not over, and its series of variants BA.1, BA.2, BA.2.12.1, BA.4 and BA.5 are setting off a new wave of epidemics around the world. And the Delta variant does not seem to be reconciled to being stole the limelight by Omicron, and is quietly accumulating power and spreading it secretly, intending to “make a comeback”.


Omicron BA.2.12.1 is “taking a firm foothold” in the United States.

BA.2.12.1 is a descendant of the 2019-nCoV Omicron subtype variant BA.2, which is currently spreading rapidly in the United States.

According to U.S. media reports, in February, two new and more contagious cases of the new coronavirus variant were identified in the northeastern United States. They are exactly the subtypes of the Ormicon strain variant BA.2 known as BA.2.12.1 and BA.2.12.2. These two subtype variants accounted for only 1.5% of new sequencing-positive cases until March 19, after which they began to spread rapidly. New York State public health officials warn that BA.2 is at least 30% more transmissible than BA.1, while BA.2.12.1 is thought to be 23%-27% more transmissible than BA.2.

During the week of April 16-23,BA.2.12.1 appeared to be more dominant of the two variants, with the proportion of cases caused by this variant increasing from 19.6% to 28.7% in the United States. According to data released by the U.S. Centers for Disease Control and Prevention (CDC) on May 3, BA.2.12.1 has accounted for 36.5%. In the past two weeks, the increase has been close to 100%. CDC Director Rochelle Valensky said additional evaluations are currently underway to understand the impact of BA.2.12.1 on vaccine effectiveness.

“BA.2 has 53 mutations, 29 of which are in the spike protein,” said Dr. Angela Blanche, co-principal investigator in the Division of Vaccine Therapeutics and Evaluation at the University of Rochester Medical Center. Enhanced ability to transmit. The BA.2.12.1 subtype also has this enhanced ability to replicate and transmit from person to person… seems to be the dominant variant in the U.S. in the coming weeks.”

According to CDC estimates, BA. 2.12.2 accounts for about one-third of all cases in the United States. Currently, the cases of BA.2.12.2 are increasing exponentially. At that rate, expect to see a sharp increase in related cases nationwide in the next month or so.


Omicron BA.4 and BA.5 lead to a surge in confirmed cases in South Africa.

In addition to BA.2.12.1, two other mutant strains of Omicron, BA.4 and BA.5, have also raised concerns.

World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus said at a press conference in Geneva on the 4th that two subtypes of the Omicron strain, BA.4 and BA.5, were responsible for the recent surge in cases in South Africa. Tedros said it was too early to determine whether the BA.4 and BA.5 subtypes caused more severe symptoms, but they were another proof that the new crown epidemic is not over.

WHO began tracking BA.4 and BA.5 in mid-April. BA.4 and BA.5 “have acquired a number of additional mutations that may affect their characteristics,” WHO updated its weekly epidemiology report.

In addition to the seven provinces of South Africa, Australia, Austria, Belgium, Israel, Denmark, France, Germany, Both subtype variants have also been detected in more than 20 countries, including Pakistan, the United Kingdom, the United States and Switzerland. Oliveira noted that BA.4 and BA.5 appear to be more infectious than BA.2, the two new variants “mutated in lineages that allow the virus to evade immunity.” They are expected to spark a new wave of infections and possibly surpass the protective efficacy of some vaccines. Taking into account vaccinations and Covid-19 infections, it is estimated that more than 90% of the South African population has some degree of immunity.


Cunning Omicron is “Master Player”

The constant emergence of these new variants shows how cunning Omicron is. “Omicron is a ‘master player’ in terms of its ability to evade antibody activity. It is much more efficient than all previous variants,” said Peiyong Shi, a virologist at the University of Texas at Galveston. , “It only takes one key mutation to make a complete change.”

According to the National Public Radio (NPR) report on the 4th, Shi Peiyong’s team extracted blood from people infected with the original variant of Omicron BA.1, Antibodies in the blood were checked to see if they could neutralize the new variants, including BA.2.12.2 in New York state or BA.4 and BA.5 in South Africa.


It was found that all people who had been infected with BA.1 had antibodies that could neutralize BA.1. But the neutralizing potency dropped significantly compared to the new variants (BA.2.12.2, BA.4, and BA.5), and the magnitude of the drop was largely dependent on whether the people were vaccinated.

In the unvaccinated people, the ability of their antibodies to neutralize BA.4 and BA.5 was nearly 8-fold lower than the ability to fight BA.1, the study reported. Research by the team of biophysicist Xie Xiaoliang at Peking University also shows that Omicron can evolve mutations to specifically evade immunity caused by BA.1 infection.


Delta wants to ‘make a comeback’

According to the “Times of Israel” report on the 4th, a new Israeli study shows that there is the possibility of another wave of global epidemics in the northern hemisphere this summer and the new coronavirus delta strain may make a comeback, posing a bigger threat than expected.

The peer-reviewed study, based on surveillance results of sewage in Israel, revealed not only the prevalence of Covid-19 cases, but also their variants. The study showed that even with high levels of the Omicron variant, the delta variant continued to spread covertly.

After monitoring the patterns of the two variants, the researchers concluded that Omicron and its sub-variants may disappear soon, but Delta has shown such resilience that it is likely to Reappear.

“In this study, we found that even when Omicron was at its highest level in the wastewater, delta continued to circulate.” Ariel Kush, a biologist at Ben-Gurion University of the Negev in Israel “Our models suggest that even though Omicron is dying, Delta is surviving and potentially ‘making a comeback,’ Marlow said. Kushmaro and colleagues report in the “journal Science of the Total Environment”, according to the analytical model, Omicron’s level is expected to decrease until it is eliminated, while Delta will continue its stealthy cycle until another wave is triggered. If this were to materialize, the cryptic cycle described above could lead to a re-emergence of delta-causing waves, or the creation of new threatening mutant strains.


Best protection is still vaccination and good public practices

“Breakthrough cases are better when vaccinated,” says Siegel of the African Institute of Health. For those who were vaccinated, the effect on BA.4 and BA.5 was comparable to the potency against BA.1. The neutralizing capacity of the product has only dropped by a factor of 3. These individuals were also more capable of neutralizing BA.1. As a result, they ended up being on average 5 times more potent at neutralizing the new variant compared to people who were not vaccinated prior to infection.

Tedros insisted on the 4th: “The best way to protect people is still to be vaccinated, while also taking tried-and-true public health and social measures.” Shi Peiyong also said: “The data has shown time and time again that vaccines are still huge benefits.”

The WHO has officially recorded more than 6.2 million deaths from Covid-19 worldwide since the outbreak began, but the true number of deaths is believed to be much higher. Newly reported cases and deaths are falling globally and have now fallen to their lowest levels since March 2020. But the WHO has warned that the global drop in cases could be the result of a slash in testing for the virus.

“These trends, while welcome, don’t tell the whole story,” Tedros said, noting that in the Americas and Africa, reported cases are rising, driven by the omicron sub variant. “Many countries are basically blind to how the virus mutates,” Tedros warned. “We don’t know what’s going to happen next.”

Tedros emphasized that the reason why the BA.4 and BA.5 subtypes can be found is that Because South Africa is still insisting on vital genetic sequencing that many other countries have stopped. The South African findings suggest that “viral testing and genetic sequencing remain absolutely critical matters”.


Source: Medical Novo, Science and Technology Daily

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