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Omicron BA.2 is almost completely different from the original strain of COVID-19.
COVID-19 outbreak in China now. The most severe COVID-19 epidemic in China in the past two years is the BA.2 subtype of the new coronavirus Omicron mutant strain .
From a virological and epidemiological point of view, Omicron BA.2 is completely different from the earlier new coronavirus strains . This is a key message for all people in the epidemic. Know yourself and the enemy, and you will be safe in a hundred battles.
From the perspective of experimental design, we have considered that Omicron is not the same virus as other SARS-CoV-2, because its viral characteristics especially determine its S protein characteristics, serological characteristics, immune escape, transmission ability, The pathogenicity, clinical manifestations and epidemiological characteristics are completely different from the wild type of the new coronavirus that began to circulate at the end of 2019 .
The transmission coefficient of the new coronavirus Omicron BA.2 is as high as 9.1
Sutter Health estimated the Omicron basic transmission coefficient (R0) = 7.0, so it is estimated that the R0 of BA.2 is as high as 9.1, while the wild-type new coronavirus R0 = 2.79. R0=9.1 means that in the absence of epidemic prevention measures, one person can spread to 9 people.
Combined with the incubation period of 3 days, the doubling time is only 2-3.3 days. Therefore, there is no epidemic prevention and control measures. Visible index of this mutant strain type growth.
However, the current national growth has not shown an exponential growth, which shows that under the influence of epidemic prevention measures and various factors, the actual transmission coefficient Rt of the virus in the China is very low . From this perspective, China’s epidemic prevention measures are effective.
Omicron has a very strong immune escape
The R0 of Omicron BA.1 has reached 7.0, which makes the transmission coefficient of Omicron reach the level of highly contagious mumps. But mumps vaccination can provide durable immunity, while Omicron can cause immune escape. The serological characteristics of it and the original wild-type SARS-CoV-2 used in the vaccine are completely different because of the 32 mutations in the Omicron S protein.
Therefore, compared with the original wild type, Omicron is equivalent to two different serotypes of influenza virus with antigenic drift .
From the clinical point of view of infected people, Omicron mainly causes asymptomatic infection in many countries.
In South Africa, 85.3% of infections are asymptomatic; in the UK, where vaccination rates are high, the real-world fatality rate is already lower than influenza; and two years ago, the fatality rate caused by the original wild type of SARS-CoV-2 was 34- 68 times .
In addition , Omicron has obvious nasal tropism and lacks pulmonary tropism .
Therefore, these reconfirmed that Omicron and SARS-CoV-2 original wild type caused almost two different diseases.
The R0 of the original strain is 2.79, so the public health method of dynamic clearing is effective; but as R0 rises to 9.1, dynamic clearing faces more and more challenges. This is also because some previous “precise epidemic prevention” was effective, but now it is difficult to key reasons for success.
The new coronavirus Alpha mutant replaces the original wild type, Delta replaces Alpha, Omicron BA.1 replaces Delta, and BA.2 is replacing BA.1.
The basic transmission coefficient of Omicron BA.2 is as high as 9.1, which means extremely high infectivity and great difficulty in prevention and control. At the same time, vaccination has become increasingly difficult to prevent infection, and the proportion of asymptomatic infections has also increased significantly; meaning that occult infections are prone to occur.
Faced with this situation, only timely vaccination . In particular, please confirm vaccination information with the elderly at home to help them complete booster vaccinations in a timely manner.
Boosting vaccination not only helps the elderly reduce the risk of severe illness, but also helps young people meet the opening day as soon as possible. The timely vaccination of the elderly is not only the cornerstone of maintaining family health, but also the foundation for society to dare to let go.
(source:internet, reference only)