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What is stealth omicron variant? China battles biggest Covid outbreak in 2 years


What is ‘Stealth Omicron’ Variant?

According to reports, much of the current outbreak is being driven by the variant commonly known as “stealth omicron” or the B.A.2 lineage of the Omicron variant.

The UK Health and Security Agency (UKHSA) announced it is investigating a sub-lineage of the omicron coronavirus variant—known as BA.2 and named by some scientists as “stealth omicron”.

The “stealth omicron” variant has been reported to spread faster than the original omicron, which itself spread faster than the original virus and other variants, according to early research.

Omicron variant had fueled the third wave of the pandemic that affected the world.

The World Health Organization (WHO) does not yet consider BA.2 to be a “variant of concern” but is continuing to monitor its spread. BA.2 is beginning to replace the original Omicron strain in many countries.

According to reports, it is now the dominant variant in Denmark, which recorded more than 50,000 new infections in just one day last week. BA.2 also appears to be the major Omicron lineage in parts of India and the Philippines. It has already caused about 250 cases in the United States and been identified in more than half the states.

The BA.2 subvariant likely arose from a common ancestor around the same time as the original Omicron, also known as BA.1, so it is not a descendent but a sibling, says Cornelius Römer, a bioinformatician at the Biozentrum of the University of Basel in Switzerland.

The BA.2 has been sometimes dubbed a stealth variant because it is missing key mutations in its spike protein that are necessary for rapid PCR tests to distinguish it from previous variants, such as Delta. This difference also may be why BA.2 escaped attention earlier.

The two Omicron lineages have evolutionary divergences from each other than the differences between the original virus and the Alpha variant, the first variant of concern. “BA.2 shares over 30 mutations with BA.1, but it also has 28 unique mutations,” says Shay Fleishon, an evolutionary geneticist and advisor to the Central Virology Laboratory in Israel.

Stealth Omicron cases in China

The National Health Commission reported 1,337 locally transmitted cases in the latest 24-hour period, including 895 in the industrial province of Jilin. A government notice said that police permission would be required for people to leave the area or travel from one city to another.

In Beijing, several buildings were sealed off over the weekend. Residents said they were willing to follow the zero-tolerance policies despite any personal impact.

The hard-hit province sent 7,000 reservists to help with the response, from keeping order and registering people at testing centers to using drones to carry out aerial spraying and disinfection, state broadcaster CCTV reported.

Hundreds of cases were reported in other provinces and cities along China’s east coast and inland as well. Beijing, which had six news cases, and Shanghai, with 41, locked down residential and office buildings where infected people had been found.

“Every day when I go to work, I worry that if our office building will suddenly be locked down then I won’t be able to get home, so I have bought a sleeping bag and stored some fast food in the office in advance, just in case,” said Yimeng Li, a Shanghai resident.

While mainland China’s numbers are small compared to many other countries, and even the semi-autonomous city of Hong Kong, they are the highest since Covid-19 killed thousands in the central city of Wuhan in early 2020. No deaths have been reported in the latest outbreaks.

Hong Kong on Monday reported 26,908 new cases and 249 deaths in its latest 24-hour period. The city counts its cases differently than the mainland, combining both rapid antigen tests and PCR test results.

The city’s leader, Carrie Lam, said authorities would not tighten pandemic restrictions for now. “I have to consider whether the public, whether the people would accept further measures,” she said at a press briefing.

Mainland China has seen relatively few infections since the initial Wuhan outbreak as the government has held fast to its zero-tolerance strategy, which is focused on stopping transmission of the coronavirus by relying on strict lockdowns and mandatory quarantines for anyone who has come into contact with a positive case.

The government has indicated it will continue to stick to its strategy of stopping transmission for the time being.

Officials on Sunday locked down the southern city of Shenzhen, which has 17.5 million people and is a major tech and finance hub that borders Hong Kong. That followed the lockdown of Changchun, home to 9 million people in Jilin province, starting last Friday.

On Monday, Zhang Wenhong, a prominent infectious disease expert at a hospital affiliated with Shanghai’s Fudan University noted in an essay for China’s business outlet Caixin, that the numbers for the mainland were still in the beginning stages of an “exponential rise.”

China’s vast passenger rail network said it would cut service significantly, and both China Railway and airlines said they would offer free refunds to people who had already bought tickets. Shanghai suspended bus service to other cities and provinces.

Shanghai has recorded 713 cases in March, of which 632 are asymptomatic cases. China counts positive and asymptomatic cases separately in its national numbers. Schools in China’s largest city have switched to remote learning.

“I think only when the epidemic is totally wiped out can we ease up,” said Tong Xin, 38, a shop owner in the Silk Market, a tourist-oriented mall in the Chinese capital.

“If our country opens up quickly now, it will cause a large number of infections in people in a short period of time,” Zhang wrote. “No matter how low the death rate is, it will still cause a run on medical resources and a short term shock to social life, causing irreparable harm to families and society.”

Risk factor

The rapid spread of BA.2 in China is worrisome for the world. Most countries have already had three waves of Covid-19 variants and this virus may just raise a chances of fourth wave. ‘Stealth Omicron’ can become new challenge for health experts and also for the world.



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