Workers rush to build a makeshift hospital at Pazhou International Convention and Exhibition Center in Guangzhou, South China's Guangdong Province, on Monday. Photo: VCG

China has reported the first case of Omicron subvariant BA.2.12.1, a mutation that has shown transmissibility that is about 23-27 percent higher than that of BA.2, in South China's Guangdong Province, according to a weekly report issued by the Chinese Center for Disease Control and Prevention (China CDC). 

The patient, a 27-year-old Chinese male, arrived on international flight KQ880 from Nairobi, Kenya in Guangzhou on April 23. All passengers were transferred to a quarantine hotel for the routine 14-day medical observation after landing. 

The patient, having received full vaccination and denying exposure to other infected cases in the previous 14 days, tested positive for COVID-19 on April 27. After diagnosis, he was transferred to Guangzhou Eighth People's Hospital for treatment.

On April 30, the virus sequence from the patient's nasal swab sample showed that he was infected with the Omicron subvariant BA.2.12.1. The sequence has been submitted to the National Genomics Data Center for further studies. 

The World Health Organization (WHO) reminded countries to closely monitor the subvariant on May 4. Compared with other Omicron variants, BA.2.12.1 shows stronger resistance to immune reaction, even after individuals have had a booster dose. 

"This suggests that even if a person has been infected with coronavirus before or has been vaccinated, s/he may still get infected with this subvariant. Vaccination, however, will to a large extent prevent the patient from developing severe symptoms," a senior expert with the China CDC told the Global Times on condition of anonymity on Tuesday.

The fast spread of the subvariant has led to the resurgence of the epidemic in many parts of the US, and cases have been reported in at least 23 countries and regions, WHO's technical lead on COVID Maria Van Kerkhov said during a Live Q&A on May 11.

In some parts of the US, BA.2.12.1 has already become the dominant subvariant. In the states of New York and New Jersey, the strain is responsible for 66 percent of cases, US media reported last week. 

"The higher transmission rate suggests that, if the basic reproduction number (R0) for Omicron BA.2 is 10, then that of BA.2.12.1 will be 12-13, indicating that one case of the new mutation can infect 12-13 people," the China CDC expert noted. 

While the subvariant has been found in China, experts said the public do not need to worry too much, as China's strict anti-epidemic measures and early detection can effectively control the virus spread.