China is tracking ‘Orthrus’ – an emerging, more transmissible Covid variant

China’s CDC says variant, also known as CH. 1.1, unlikely to cause new outbreaks soon
US study found CH. 1.1 ‘highly resistant’ to mRNA vaccines

Coronavirus China

Hayley Wong

Published: 5:00pm, 1 Feb 2023

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The Omicron subvariant CH. 1.1, also known as “Orthrus”, which is becoming increasingly prevalent in Britain and the United States, is unlikely to cause another wave of outbreaks in the mainland in the near future, Chinese health authorities said.

The most prevalent variants in China continue to be BA. 5.2 and BF. 7, but 24 cases of CH. 1.1, a more transmissible subvariant, have been reported in China in the past three months, authorities said.

“Despite an increased ability to resist immune responses and a higher transmissibility, which might increase breakthrough infection and reinfection risks, the population in China has a high level of neutralising antibodies,” the Chinese Centre for Disease Control and Prevention (CDC) said in a statement on Tuesday night.

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“There is a certain effect on cross protection [the degree of immunity conferred by previous infections], and it will not cause a large-scale domestic outbreak in the short term,” authorities said in the statement, adding that vulnerable groups including elderly and unvaccinated people should step up protection.

Orthrus, named after a two-headed dog from Greek mythology that was killed by the hero Heracles, has raised global concern because of a particular mutation that it carries – known as L452R – which experts believe increases the variant’s immunity to current vaccines, similar to the mutation in the earlier Delta variant.

However, the CDC said that the same mutation found in CH. 1.1 is also present in other subvariants like BA. 5.3 and BA. 5.1.3, and it is still unclear if the lineage could cause more severe symptoms of the disease.

The first case of CH. 1.1 in China was detected in November in the city of Tianjin, near Beijing, and was imported from Thailand, according to authorities.

The 23 other cases were imported from 15 other regions, and no local cases have been reported so far.

The emerging variant was first identified in India last July and is now present in 67 countries, accounting for more than 6 per cent of genomic sequence data reported globally, authorities said, citing statistics from international genomic database GISAID.

As of the first week of January, CH. 1.1 infections and its sub lineage accounted for about 25 per cent of the total infections in the UK, according to the latest infection survey released by the country’s Office for National Statistics.

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While XBB. 1.5 continues to dominate cases in the US, CH. 1.1 is now the fifth most prevalent lineage in the country, according to official data.

According to a preprint paper published by researchers at the Ohio State University, CH. 1.1’s ability to evade neutralising antibodies is “extraordinary”.

Their study of serums, the part of blood that contains antibodies, found that CH. 1.1 variants are “highly resistant” to both monovalent and bivalent mRNA vaccinations, as well as the antibodies produced by previous BA.4 and BA.5 infections.

Chen Cao, a researcher at China’s CDC, reaffirmed on Monday that BA. 5.2 and BF. 7 remain the dominant variants in China, adding that no other “advantageous variants” have been found so far that could become dominant.