Has the new coronavirus strain CH.1.1 entered my country? Will it cause new infections? Authoritative interpretation——

On January 30, according to the latest data from the Centers for Disease Control and Prevention (CDC), the US Centers for Disease Control and Prevention is tracking a new coronavirus strain called CH.1.1. CH.1.1 accounts for 1.5% of US cases, ranking fifth. According to data from the epidemic tracking data website Outbreak.info, many cases of CH.1.1 have now appeared in New Zealand. Other hotspots include Papua New Guinea, Cambodia, Ireland, etc. The strain has been detected in more than 60 countries and 51 states in the United States.

What is CH.1.1? Will it be more pathogenic? The Institute of Viral Diseases of the Chinese Center for Disease Control and Prevention conducted an analysis:

1. What is the Omicron variant CH.1.1?

CH.1.1 belongs to the sixth-generation subbranch of the Omicron variant BA.2.75. The latest research shows that the immune escape ability of CH.1.1 has increased due to the addition of multiple mutation sites. At the same time, a new mutation site (L452R) was once a characteristic mutation site of the Delta variant. But it is worth noting that this mutation site also exists in many other Omicron variant subbranches, such as BA.5.3 and BA.5.1.3.

Since November 2022, the proportion of CH.1.1 in the prevalent strains of the new coronavirus in the United States has been on the rise. In the fourth week of 2023, CH.1.1 ranked fifth among the prevalent strains in the United States, second only to XBB.1.5, BQ.1.1, BQ.1 and XBB variants.

2. Will CH.1.1 become more pathogenic?

At present, the pathogenicity of the CH.1.1 variant has not been increased, and further attention is still needed. Generally, after a new strain appears, the number of infected cases needs to reach a certain scale and last for a period of time before a preliminary judgment can be made on whether the pathogenicity of the new strain has changed.

3. CH.1.1 Global epidemic characteristics

According to the sequences collected 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 subbranches accounted for more than 6% of the global sequence number. As of January 30, 2023, it has been monitored and found in 67 countries or regions, mainly in the United Kingdom, Denmark, Singapore and other countries, accounting for about 25% of the new coronavirus sequences uploaded in the United Kingdom in the past month.

4. CH.1.1 Detection in my country

On November 13, 2022, my country detected the CH.1.1 evolutionary branch for the first time from a sample of a Thai imported case reported by Tianjin (sampled on November 10, 2022) through genome sequencing. As of January 30, 2023, a total of 24 imported cases of CH.1.1 and its sub-branches have been monitored and found. The sources of imported cases involved 15 countries or regions. No local infection cases of CH.1.1 and its sub-branches have been monitored.

5. Can CH.1.1 trigger a second round of infection?

Although the immune escape ability and transmission advantage of the CH.1.1 variant have been further enhanced, leading to an increased risk of breakthrough infection and reinfection, high levels of neutralizing antibodies already exist in most people in my country, which provide a certain degree of cross-protection against CH.1.1. CH.1.1 will not cause a large-scale local epidemic in the short term. Vulnerable groups (people over 65 years old, patients with underlying diseases, and those who have not been vaccinated) and uninfected people still need to strengthen personal protection.

6. How to deal with CH.1.1?

Adhere to personal protection, maintain good hygiene habits, and do not believe unconfirmed online reports.

Source: Beijing Daily, China CDC WeChat official account, People's Daily Health Client