Beijing, March 3 (Zhongxin.com) (Wei Xianghui) According to the latest weekly report released on the website of the Chinese Center for Disease Control and Prevention, cases of co-infection of Omicron BA.18.5.2 and BF.48.7 subtypes have been found for the first time in China. Why do co-infections occur? Does it increase the risk of virus mutation and transmission?

The first co-infection case of two subtypes of Omicron appeared in China

On March 3, the website of the Chinese Center for Disease Control and Prevention released the latest "China CDC weekly", and on February 17, co-infection with the Omicron strain was detected in samples collected and sent for testing in the Third Affiliated Hospital of Chongqing Medical University.

On 2022 December 12, the patient reported poor appetite and tested positive for Covid infection on 23 December. On January 12, 29, the patient developed chills and fever (body temperature 2023.1°C), accompanied by cough symptoms, was admitted to Yunyang County Traditional Chinese Medicine Hospital but did not improve significantly, and was discharged on January 4. On January 38, the patient was admitted to the Department of Infectious Diseases, the Third Affiliated Hospital of Chongqing Medical University. From January 9 to February 1, eight nucleic acid tests were positive.

The researchers took upper respiratory tract samples from the patient on January 2023 and February 1, 28, named YB2 and YB7, respectively, which formed a separate clade distinct from the Omicron subvariants BA.20230158.20230202.5 and BF.2.48. Mutation site analysis showed that both samples contained specific defining sites of Omicron subvariants BA.7.14.5 and BF.2.48, and the patients were simultaneously infected with Omicron subvariants BA.7.14.5 and BF.2.48.

The main variant of the new coronavirus currently circulating in Chongqing is BA.5.2.48 (>90%), followed by BF.7.14 (about 3.8%), the report said. So far, there have been no reports of co-infection of BA.5.2.48 and BF.7.14 in China, especially in Chongqing, where the proportion of BF.7.14 is relatively low.

Image source: China CDC Weekly Report

Co-infection may be associated with immunocompromised patients

According to the weekly report information, in this case, the patient is a 67-year-old woman with a history of malignant tumors, has received chemotherapy, radiotherapy, targeted therapy and other treatments in the past 6 months, but has no other underlying diseases, smoking history or drinking habits, and has received two doses of the new crown vaccine.

Her family and neighbors were found infected in late December, indicating potential exposure, the report said. During her two hospital stays, she may have been exposed to other people infected with the virus.

Lu Mengji, a professor at the Institute of Virology at the University of Essen School of Medicine in Germany, told Chinanews.com that the premise of co-infection is that they have been exposed to different strains. There are currently many different variants circulating around the world, and individuals can indeed be infected with different variants.

He analyzed that this patient has been positive for a long time after infection, and it may be that he has an immune deficiency and cannot clear the virus within 1 to 2 weeks like others.

Li Tong, chief physician of the Department of Respiratory and Infectious Diseases of Beijing You'an Hospital affiliated to Capital Medical University, once believed that the probability of co-infection is extremely low, which is mostly related to the patient's low own immunity.

"The likelihood of contracting two viruses at the same time within two weeks is very small." He explained to Chinanews.com that most of this situation occurs in immunocompromised people, such as lymphoma patients, who may not be able to clear the virus for two or three months, and if they are exposed to other strains during this period, co-infection may occur.

Data map: Photo by An Yuan, Department of Critical Care Medicine of the hospital

Surveillance of novel coronavirus variants needs to be strengthened

In terms of the risk of the spread of co-infection, Li Tong once believed that the situation of a co-infected patient transmitting two viruses to one person at the same time generally does not occur.

"When the two viruses in the body are excreted, they are not necessarily excreted at the same time, and if they are immunologized, even if they are infected with two viruses, they can be cleared by the immune system in the body in about a week, and they may not continue to spread." He said that now that immune barriers have been established in most areas, most people are still resistant after infection. There is no need to worry unduly about the further spread of co-infection.

Li Tong has mentioned that the next thing researchers need to continue to pay attention to is whether the virus will further mutate in patients with co-infection, or recompose to produce some new strains.

The latest weekly report released by China CDC also mentioned that the surveillance of new coronavirus variants should be promoted as an important strategy to identify co-infection and recombinant cases. As the risk of co-transmission of variants in a region increases, surveillance of coronavirus variants, especially for key immunocompromised populations, is becoming increasingly important. (End)