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　　What is Omicron variant strain CH.1.1?

　　CH.1.1 belongs to the sixth generation subclade of the Aomecron mutant strain BA.2.75.

The latest research shows that due to the addition of multiple mutation sites, the immune escape ability of CH.1.1 is increased.

At the same time, a newly added mutation site (L452R) was once a characteristic mutation site of the delta variant.

However, it is worth noting that this mutation site also exists in many other subclades of Omicron mutant strains, such as BA.5.3 and BA.5.1.3.

　　From November 2022 to the present, the proportion of CH.1.1 among the epidemic strains of the new coronavirus in the United States is on the rise.

In the fourth week of 2023, the proportion of CH.1.1 strains prevalent in the United States is the fifth, second only to XBB.1.5, BQ.1.1, BQ.1 and XBB mutant strains.

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　　CH.1.1 Will it be more pathogenic?

　　At present, there is no enhanced pathogenicity of the CH.1.1 mutant strain, and further attention is still needed.

Generally, after a new strain emerges, the infection cases need to reach a certain scale and last for a period of time before we can initially judge whether the pathogenicity of the new strain has changed.

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　　CH.1.1 Global epidemic characteristics

　　According to the sequences included in the GISAID database, CH.1.1 was first collected and discovered in India on July 8, 2022.

In the past month, CH.1.1 and its sub-branches accounted for more than 6% of the global sequences.

As of January 30, 2023, it has been detected in 67 countries or regions, and it is mainly prevalent in the United Kingdom, Denmark, Singapore and other countries. It accounts for about 25% of the new coronavirus sequences uploaded in the United Kingdom in the past month.

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　　CH.1.1 Detection situation in my country

　　On November 13, 2022, my country detected the CH.1.1 evolutionary branch for the first time from a sample of an imported case from Thailand (sampled on November 10, 2022) reported by Tianjin through genome sequencing.

As of January 30, 2023, a total of 24 imported cases of CH.1.1 and its subclades have been detected.

The source of imported cases involves 15 countries or regions.

Indigenous infection cases of CH.1.1 and its subclades were not detected.

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　　Can CH.1.1 trigger a second round of infection?

　　Although the immune escape ability and transmission advantages of the CH.1.1 mutant strain have been further enhanced, leading to an increased risk of breakthrough infection and reinfection, most people in my country already have high levels of neutralizing antibodies, which have a certain cross-protective effect on CH.1.1. CH.1.1 will not cause a large-scale local epidemic in the short term.

Vulnerable groups (the elderly over 65 years old, patients with underlying diseases and those who have not been vaccinated) and uninfected groups still need to strengthen personal protection.

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　　How to deal with CH.1.1?

　　Adhere to personal protection, maintain good hygiene habits, and don't believe unverified online reports.