An imported human case with the SARS-CoV-2 omicron subvariant BA.2.75 in Yunnan province, China.

The Omicron variants spread rapidly worldwide after being initially detected in South Africa in November 2021. It showed increased transmissibility and immune evasion with far more amino acid mutations in the Spike (S) protein than the previously circulating variant of concern (VOC). Notably, on 15 July 2022, we monitored the first VOC/Omicron subvariant BA.2.75 in China from an imported case. Moreover, nowadays, this subvariant still is predominant in India. It has nine additional mutations in the S protein compared to BA.2, three of which (W152R, G446S, and R493Q reversion) might contribute to higher transmissibility and immune escape. This subvariant could cause wider spread and pose a threat to the global situation. Our timely reporting and continuous genomic analysis are essential to fully elucidate the characteristics of the subvariant BA.2.75 in the future.

The Epidemiological Features of the SARS-CoV-2 Omicron Subvariant BA.5 and Its Evasion of the Neutralizing Activity of Vaccination and Prior Infection.

From December 2021 to May 2022, the Omicron BA.1 and BA.2 subvariants successively became the most dominant strains in many countries around the world. Subsequently, Omicron subvariants have emerged, and Omicron has been classified into five main lineages, including BA.1, BA.2, BA.3, BA.4, BA.5, and some sublineages (BA.1.1, BA.2.12.1, BA.2.11, BA.2.75, BA.4.6, BA.5.1, and BA.5.2). The recent emergence of several Omicron subvariants has generated new concerns about further escape from immunity induced by prior infection and vaccination and the creation of new COVID-19 waves globally. In particular, BA.5 (first found in southern Africa, February 2022) displays a higher transmissibility than other Omicron subvariants and is replacing the previously circulating BA.1 and BA.2 in several countries.

The emergence and epidemic characteristics of the highly mutated SARS-CoV-2 Omicron variant.

Recently, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant (B.1.1.529) was first identified in Botswana in November 2021. It was first reported to the World Health Organization (WHO) on November 24. On November 26, 2021, according to the advice of scientists who are part of the WHO's Technical Advisory Group on SARS-CoV-2 Virus Evolution (TAG-VE), the WHO defined the strain as a variant of concern (VOC) and named it Omicron. Compared to the other four VOCs (Alpha, Beta, Gamma, and Delta), the Omicron variant was the most highly mutated strain, with 50 mutations accumulated throughout the genome. The Omicron variant contains at least 32 mutations in the spike protein, which was twice as many as the Delta variant. Studies have shown that carrying many mutations can increase infectivity and immune escape of the Omicron variant compared with the early wild-type strain and the other four VOCs. The Omicron variant is becoming the dominant strain in many countries worldwide and brings new challenges to preventing and controlling coronavirus disease 2019 (COVID-19). The current review article aims to analyze and summarize information data about the biological characteristics of amino acid mutations, the epidemic characteristics, immune escape, and vaccine reactivity of the Omicron variant, hoping to provide a scientific reference for monitoring, prevention, and vaccine development strategies for the Omicron variant.

The Global Epidemic of the SARS-CoV-2 Delta Variant, Key Spike Mutations and Immune Escape.

During the COVID-19 pandemic, SARS-CoV-2 variants have emerged and spread worldwide. The Delta (B.1.617.2) variant was first reported in India in October 2020 and was classified as a "variant of concern (VOC)" by the WHO on 11 May, 2021. Compared to the wild-type strain, several studies have shown that the Delta variant is more transmissible and has higher viral loads in infected samples. COVID-19 patients infected with the Delta variant have a higher risk of hospitalization, intensive care unit (ICU) admission, and mortality. The Delta variant is becoming the dominant strain in many countries around the world. This review summarizes and analyses the biological characteristics of key amino acid mutations, the epidemic characteristics, and the immune escape of the Delta variant. We hope to provide scientific reference for the monitoring and prevention measures of the SARS-CoV-2 Delta variant and the development strategy of a second-generation vaccine.

The global epidemic of SARS-CoV-2 variants and their mutational immune escape.

During the COVID-19 pandemic, genetic variants of SARS-CoV-2 have been emerging and spreading around the world. Several SARS-CoV-2 endemic variants were found in United Kingdom, South Africa, Japan, and India between 2020 and April 2021. Studies have shown that many SARS-CoV-2 variants are more infectious than early wild strain and produce immune escape. These SARS-CoV-2 variants have brought new challenges to the prevention and control of COVID-19. This review summarizes and analyzes the biological characteristics of different amino acid mutations and the epidemic characteristics and immune escape of different SARS-CoV-2 variants. We hope to provide scientific reference for the monitoring, prevention, and control measures of new SARS-CoV-2 variants and the development strategy of the second-generation vaccine.

Undocumented Migrants Reintroducing COVID-19, Yunnan Province, China.

To limit the spread of severe acute respiratory syndrome coronavirus 2, the government of China has been monitoring infected travelers and minimizing cold-chain contamination. However, other factors might contribute to recurring outbreaks. We analyze the role of undocumented migrants as potential transmitters of severe acute respiratory syndrome coronavirus 2 in China.