New coronavirus strains in Guangdong and Sichuan: Omicron BA.4 and Omicron BA2

Chinese media reported today, citing the China Center for Disease Control and Prevention Weekly Report, the discovery of new subtypes of the Omicron coronavirus strain in China.


As reported, on May 4, according to the results of gene sequencing, the first imported case of the BA.4 subtype "omicron" strain of coronavirus was confirmed.

The patient arrived in Guangzhou, Guangdong province from Amsterdam, the Netherlands on April 29. After the first nucleic acid test at the airport, he was sent to a quarantine hotel along with all the passengers on the flight for a scheduled 14-day medical observation. On April 30, the nucleic acid test was positive, and the nasopharyngeal swab sample was immediately retested on May 1 and reported positive.


It is reported that the patient was fully vaccinated before flying to China and underwent a 14-day quarantine. After the diagnosis was made, the patient was referred to Foshan Fourth People's Hospital for treatment.


The results of gene sequencing showed that a total of 30 sites of amino acid mutations and 5 deletions were identified in the BA.4 variant spike protein gene.

On May 4, the World Health Organization recalled the close monitoring of the BA.4 Omicron subtype variant. Variant BA.4 has faster transmission among those infected, BA.4 is causing a new wave of outbreaks in South Africa and rapidly replacing BA.2. Since the first week of April 2022, more than 50% of sequenced cases in South Africa have been infected with BA.4.


On May 21, Guang'an, Sichuan Province, reported 12 new locally confirmed cases and 34 new asymptomatic infections. According to the results of whole genome sequencing of nasal and throat swab samples from the first three asymptomatic infections in Guang'an, the source of the virus in Guang'an was traced to a new variant of the coronavirus Omicron BA2.2.


According to an epidemic prevention and control press conference in Guang'an City, Sichuan Province, the new variant of the Omicron BA2.2 coronavirus strain has a high viral load, rapid transmission, strong cover-up, and many asymptomatic infections.


A report from the "Weekly Report of the Chinese Center for Disease Control and Prevention" states that a deletion of one gene in the BA2.2 variant reduces the ability to express antigens and causes significant expression of pro-inflammatory factors, while another deletion can lead to mild infection and cause a more effective immune response to the new coronavirus. However, how this variant affects the infectivity and pathogenicity of the virus requires additional epidemiological studies and results of genetic monitoring.