Omicron BA.2 Lineage, the “Stealth” Variant: Is It Truly a Silent Epidemic? A Literature Review

Abstract

The epidemic curve of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is silently rising again. Worldwide, the dominant SARS-CoV-2 variant of concern (VOC) is Omicron, and its virological characteristics, such as transmissibility, pathogenicity, and resistance to both vaccine- and infection-induced immunity as well as antiviral drugs, are an urgent public health concern. The Omicron variant has five major sub-lineages; as of February 2022, the BA.2 lineage has been detected in several European and Asian countries, becoming the predominant variant and the real antagonist of the ongoing surge. Hence, although global attention is currently focused on dramatic, historically significant events and the multi-country monkeypox outbreak, this new epidemic is unlikely to fade away in silence. Many aspects of this lineage are still unclear and controversial, but its apparent replication advantage and higher transmissibility, as well as its ability to escape neutralizing antibodies induced by vaccination and previous infection, are rising global concerns. Herein, we review the latest publications and the most recent available literature on the BA.2 lineage of the Omicron variant.

Clinico-demographic profile of COVID-19 positive patients - first wave versus second wave – an experience in north-east India

“…The findings from this study where we have seen spike in cases coinciding with the return of the migrant population bears causal relationship to community transmission in the state. It may be recommended to have more stringent quarantine and isolation practices like the ones that were in place during the FW whenever a fresh influx of migrants are anticipated especially when the 'stealth omicron' variant, a sub-lineage for the omicron variant is causing the worst COVID outbreak after Wuhan in China and South Korea and is a threat to cause the fourth outbreak in India [3]. It has already caused explosive outbreaks in South Africa and the UK and is threatening to do the same in India [45].…”

“…The data generated from this study may be used in various mathematical models to make reliable future projections of the timings of possible surge of infection and identifying the vulnerable population proportions, in addition to understanding the disease trend. Our study will add to existing knowledge and may further aid the local health authorities to make data driven north-east (NE)-centric guidelines and ramp up preparedness to tackle this pandemic, especially with the 'stealth omicron' variant causing explosive outbreaks in China and Korea [3].…”

Emergence of New SARS-CoV2 Omicron Variants after the Change of Surveillance and Control Strategy

“…This was also the beginning of the circulation of BA.2. After this moment, the BA.2 Omicron variant became the majority in the world, constituting half of the sequences uploaded to GISAID in the last month [ 2 , 3 , 13 , 14 , 15 ]. On average, BA.2 variants appeared only three months after being detected in the world, while BA.1 variants took five months.…”

“…In fact, more than 100 sub-linages had been designed in May 2022 ( (accessed on 30 May 2021)). Because there is a geographic distribution of variants, local circulation data are as important as national level data [ 13 , 15 , 19 , 20 , 21 , 22 ].…”

Comparative analysis of prevention and control measures toward COVID-19 epidemic between Shanghai and Beijing

“…2.2, which has the characteristics of a short incubation period, rapid transmission, strong infectivity, strong concealment, and immune escape ( 5 ). Studies have shown that the R0 (basic reproduction number) of Omicron BA.1 is 9.5, the transmission ability of BA.2 is 1.4 times that of BA.1, and R0 is about 13.3 ( 6 ).…”