The new variants of the Omiljunn lineage, BA.4 and BA.5, are behind a new wave of COVID-19 in South Africa, but they may also be a sign that the future COVID-19 epidemic will become more predictable.
On May 6, local time, an article in Nature (www.nature.com) quoted virologists as saying that important new variants of the new coronavirus seem to appear every six months, which may be the cyclical transmission pattern that will be fixed in the future new crown epidemic.
Nearly six months after researchers in South Africa discovered the new coronavirus Olmi kerong variant, two offshoots of the Semikron strain once again led to a surge in COVID-19 cases in the country.
Several studies published over the past week have shown that the new Variants of Omikejong, known as BA.4 and BA.5, are more contagious than earlier Omiljun viruses, enabling escaping people to develop partial immune protection from infection with the early virus and vaccination.
Penny Moore, a virologist at the University of the Witwatersrand in Johannesburg, South Africa, said: "It's safe to say that South Africa is making a comeback, and it seems to be driven entirely by BA.4 and BA.5." Her team is studying these new variant strains. "The number of infections is growing like crazy. In my lab, six people took sick leave. ”
However, scientists say it is unclear whether BA.4 and BA.5 will lead to a sharp increase in hospitalizations in South Africa or elsewhere. Previous waves of Infections in Omikeron and vaccinations have given the population a high level of immunity, which may blunt the damage caused by the new variant of the new coronavirus.
In addition, the rise of BA.4 and BA.5, and the emergence of another variant of Omilon in North America, BA.2.12.1, may mean that COVID-19 is beginning to enter a relatively predictable pattern, with new waves of infection periodically emerging from circulating strains of the virus. Tulio de Oliveira, a bioinformatician at Stellenbosch University in South Africa, said" "This is the first sign that the virus mutation is starting to become different from the past," and in the first two years of the new crown epidemic, the virus mutation appears to have appeared suddenly.
The new variant strains have more propagation advantages
By analyzing the viral genomes of clinical samples, de Oliveira and his colleagues found that BA.4 and BA.5 appeared in mid-December 2021 and early January 2022, respectively. Infection rates with both variants have been rising since then and now account for 60%-75% of COVID-19 infections in South Africa. The researchers also found both variants of the virus in more than a dozen other countries, most of them in Europe.
On the basis of the increase in the number of BA.4 and BA.5 infections in Aumicron in South Africa – in March, the average number of infections per day was 1200, compared to the current average of nearly 5000 infections per day – de Oliveira's team estimated that the transmission rate of these two variants was slightly higher than that of Aumikron BA.2 (the transmission rate of BA.2 was higher than that of The first variant of Aumiqueron, BA.1). The study, published in a medRxiv preprint, has not yet been peer-reviewed.
Jesse Bloom, a virus evolutionary biologist at the Fred Hutch Research Center in Seattle, Washington, agrees that BA.4 and BA.5 spread faster than other variants. "But it's unclear why they're more contagious," he said, "and one possibility is that they're inherently more spreadable." Another explanation is that mutant strains are more likely to escape the immune response, allowing them to infect people who are already immune to previous viruses.
Bloom added that both variants are closely related to BA.2 — though exactly how they are related is unclear. Both BA.4 and BA.5 carry a key mutation called F486V in the spike protein, which is the "key" to the new crown virus infection and the main target of the body's immune response. Previously, Bloom's team found that this mutation could help the virus variant avoid virus-blocking antibodies.
Further research also showed that BA.4 and BA.5 infections are growing, at least in part because these two variants have stronger escape immunity. A team led by Alex Sigal, a virologist at the Africa Health Research Institute in Durban, South Africa, analyzed blood samples from 39 people infected during the first wave of the Omiljung epidemic, 15 of whom had been vaccinated against COVID-19.
Experiments have shown that the antibodies in these blood samples are several times less effective at preventing cells from being infected by the BA.4 or BA.5 variant than they are at preventing infection from the original Strain of Omikeron. However, antibodies produced by people who have been vaccinated are more effective against new strains of the virus than those produced entirely as a result of BA.1 infection. The study was published in medRxiv.
Another study by Xie Xiaoliang, a virologist at Peking University, also found that antibodies produced by BA.1 infection have a weak ability to neutralize BA.4 and BA.5.
The ability of the BA.4 and BA.5 variants to escape immunity, while not surprisingly large, is "enough to cause trouble and lead to a new wave of infections," but Siegel said on Twitter that the new strains are unlikely to cause more serious illness than previous rounds of outbreaks, especially in vaccinated populations.
The number of hospitalizations in South Africa for COVID-19 infections is slowly rising — fewer than 2,000 people were hospitalized in early April, but researchers say it's too early to tell if the BA.4 and BA.5 strains will put a lot of pressure on the health care system. De Oliveira said south Africa's medical resources are relatively abundant, and the South African population has a high level of immunity.
New variants or appear every six months
While the Omikejong BA.4 and BA.5 variants have been found in several European countries and North America, the variants may not trigger a new wave of infection in these places — at least not right away. That's because the closely related BA.2 variant has just swept across Europe, so the population's immunity may still be high, Wenscelles said, "maybe they'll have a smaller advantage in Europe and a smaller wave of infections." ”
In some parts of North America, researchers have also found spike protein mutations in other Omiljung lines in the same places as mutations in the spike protein of ba.4 and BA.5 virus variants. According to research led by Peking University professor Xie Xiaoliang and a separate study by David Ho, a virologist at Columbia University in New York and inventor of the AIDS cocktail therapy, one variant called BA.2.12.1 also has the ability to escape previous immune responses from Aumicjung virus infection and vaccination.
He Dayi said that the emergence of these mutant strains shows that the Aomi Kerong family is continuing to accumulate gains by eroding immunity. "It's clear that the holes in the original Omikejong virus are gradually being filled by these new sub-variants."
Mutations produced by the coronavirus that can escape immunity will be a key driver of the wave of cyclical infections. "This may be more and more of what we're going to see in the future," Moore said.
New coronavirus mutation lineage
Unseleus and other scientists say we should not rule out other unexpected conditions for covid-19. For example, the Delta strain of the new coronavirus has not completely disappeared, and as global immunity to the Olmikron variant and its sub-variants increases, Delta's descendants may make a comeback. Regardless of their source, new important variants of the virus appear to appear about once every six months, and Wencellus noted, wondering if that's the transmission pattern that the covid-19 outbreak will fix.
"It's an interpretation of what's being observed so far," Bloom said, "but I think we should also be cautious about extrapolating general rules from a fairly short time frame." ”