Every few months in the first two years of the pandemic, we heard the name of a new variant of the coronavirus that had emerged and was even better adapted to infect or make us seriously ill. Millions of people died from one of ten variants named after Greek letters, from alpha to mu. Then in November 2021 omikron, a very different version of the virus, appeared. In the past ten months, the World Health Organization (WHO) has not announced names of new variants. So the question is: has the virus development stopped?
In the past three months, at least 300 Americans have died from COVID-19 every day, and about 50,000 new infections were reported in the US in September, caused by new omikron strains: BA.2, BA.2.12.1, BA.4 and BA.5. The infection rate among residents of nursing homes in the US is nine times higher than in late April, and by August the death rate in this group had nearly quadrupled, according to data from the AARP Public Policy Institute and the Scripps Gerontology Center at Miami University. In the UK, where the numbers often predict trends in the US, the number of symptomatic infections has risen continuously since August 27, the day with the lowest number of infections this year, according to data from the ZOE COVID-19 survey , in which patients report symptoms via an app. While the WHO has not assigned their own Greek letter to these recent omikron descendants, experts fear that the new boosters and treatments will have no effect on these variants, causing a new wave of infections and deaths.
The coronavirus is constantly mutating, there are currently more than two hundred new omikron strains and derivatives. “SARS-CoV-2 is still developing,” said Olivier Schwartz, head of the Virus & Immunity Unit at the French Institut Pasteur.
Marion Koopmans is director of the WHO Center for Infectious Diseases Collaboration and a member of the WHO team trying to identify the origins of the COVID-19 pandemic. “The situation is much better than before,” she says. But she warns that we must prepare for the next big wave as fall and winter approach. “A marathon runner doesn’t stop running before the finish line.”
New SARS-CoV-2 variants are still emerging
Every time SARS-CoV-2, the virus that causes COVID-19, multiplies, there can be a mistake in the DNA that causes it to change a little bit. These changes, called mutations, happen randomly and usually have little or no effect on the virus. If an identical mutation occurs and spreads in populations that are not in contact with each other, this indicates that the mutation is beneficial for the virus. Such mutations then form a new branch in the SARS-CoV-2 evolutionary tree. The viruses that take care of that new branch are called ‘variants’.
‘The more SARS-CoV-2 circulates, the more chance it has to mutate,’ says epidemiologist Maria van Kerkhove. She is ultimately responsible for the WHO’s response to COVID-19. Scientists also think that new omikron-like variants could develop in people with weakened immune systems. They carry the virus for a longer period of time, which means that it can undergo dozens of mutations.
Some mutations allow a variant to spread faster or make people more seriously ill. Other mutations cause the virus to change in appearance, preventing it from being picked up by the immune system after a previous infection or vaccination. These types of mutations cause approved treatments to work less well or no longer. If this happens, they will be labeled as worrisome by the WHO (variant of concernvoc) of interessant (variant of interestbutter).
In May 2021, the WHO began naming such variants based on letters of the Greek alphabet. “But WHO doesn’t name all variants,” said Anurag Agrawal, chair of the WHO’s technical advisory group for virus development, which makes recommendations on variant naming. ‘We only do this if there is a fear that a variant poses additional risks, which means that public health measures have to be taken,’ he explains.
At the moment, all omikron strains are considered voc because they all share the same properties: they spread faster than previous variants and they are resistant to previous immunity. Fortunately, an infection by a certain omikron subvariant does lead to a smaller chance of becoming infected with another subvariant. The strains are also no more dangerous than the original omikron virus, says Van Kerkhove.
Omikron variants make evolutionary leaps
The emergence of the omikron variant less than a year ago marked a major change in the evolution of SARS-CoV-2. As of November 2021, more than half of the COVID-19 infections worldwide were probably caused by one of the five omikron subvariants: BA.1, BA.2, BA.3, BA.4 and BA.5. Because omikron has been shown to be able to evade the immune response by contamination with earlier variants, some scientists, including Schwartz, believe that omikron should be considered a separate serotype of SARS-CoV-2: a virus so different from previous variants that antibodies against one insufficient protection against others. The flu virus has three serotypes: influenza A, B and C.
In recent months, omikron BA.2 has spawned a whole series of variants such as BA.2.75, BA.2.10.4, BJ.1 and BS.1. These variants, which sometimes contain dozens of mutations, are so different from the BA.2 variant from which they descend that scientists call them ‘second-generation variants’. Such variants arise through a large evolutionary leap compared to previous variants, without small intermediate steps.
From an evolutionary point of view, the recently spreading variants, such as BA.2.75, resembled the original omikron virus less than alpha, beta, gamma and delta resembled the original version, says virologist Thomas Peacock of Imperial College London. All the mutations in those earlier variants are nothing compared to those of omikron and its subvariants, he says.
‘A potentially worrisome subvariant is BA.2.75.2. This one has additional mutations compared to BA.2.75 and seems very resistant to antibodies,’ says Schwartz.
The WHO has not named these new variants after a new Greek letter, but “that certainly does not mean that no new variants have emerged since November 2021,” said immunologist Yunlong (Richard) Cao of Peking University in Beijing.
At present, BA.5 is the most common in many countries, while BA.2.75 is the most widely circulated in other countries. They are both resistant to the immune system of people who have been vaccinated or have been infected, but current vaccines may work against the variants.
‘What we now see is that the evolution continues,’ says Koopmans. This is to be expected when a virus continues to circulate on a large scale while more and more people develop an immune system in the meantime. ‘We therefore assume that even more escape variants will emerge,’ she adds.
There is debate as to how useful it is to sweep all sub-variants of omikron into one big heap. The omikron strains BA.1, BA.2, and BA.5 resembled enough in their origin to be called omikron, but according to some scientists the new variants are so different that they should be named after a new Greek letter.
“Some of those new viruses are just as genetically different as the original variants were, so the question is how useful it is to still see them as omikron variants,” Peacock said.
But the WHO working group thinks otherwise. ‘If it is determined that there is a variant or sub-variant that differs substantially from other variants or sub-variants of omikron, it is given a new name,’ says Van Kerkhove. ‘But at the moment all those sub-variants are seen as omikron, they are all vocs and they all require countries to take measures.’
Since there is no scientific evidence that the new sub-variants of omikron make people more seriously ill, the advice remains unchanged, says Agrawal.
In the meantime, early detection and treatment, the timely deployment of available resources and vaccination are needed to prevent the spread of the virus and thus the chance of new variants developing, says Van Kerkhove. “We can deal with COVID-19 in a responsible way and take simple measures to prevent the spread, such as keeping your distance, wearing masks, ventilating, washing hands and staying home when you are sick.”
This article was originally published in English on NationalGeographic.com