July 24, 2024

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BA.2.12.1 BA.4 and BA.5 All appear in Australia: 2nd highest infection rate in the world

BA.2.12.1 BA.4 and BA.5 All appear in Australia: 2nd highest infection rate in the world


BA.2.12.1 BA.4 and BA.5 All appear in Australia: 2nd highest infection rate in the world.


Australia has become one of the countries with the highest infection rates in the world as three new Omicron variants, BA.2.12.1, BA.4 and BA.5, have gathered in Australia.


The latest figures from Australia show that the country now has an average daily rate of 1,515 new infections per million people, the second highest in the world among countries with a population of more than 1 million, behind New Zealand (1,566 cases per million people). ). On May 4, the country’s largest state, Western Australia, reported 9,782 new confirmed cases of the COVID-19, with a population of 2.62 million.


BA.2.12.1 BA.4 and BA.5 All appear in Australia: 2nd highest infection rate in the world.



Australian health authorities have warned that the new coronavirus and the flu will co-occur this winter. Previously, due to the strict epidemic prevention policy against the COVID-19, influenza, which is also a respiratory infectious disease, was also greatly suppressed.

Australia has seen a sharp drop in the number of people hospitalised or dying from flu during the Covid-19 pandemic, with zero flu-related deaths in 2021. And as Australia begins to relax its epidemic prevention policies, the flu has a tendency to make a comeback.


Australian health authorities are justified in their concerns, as flu coinfection with the new coronavirus is “adding fuel to the fire”.

According to research conducted by the State Key Laboratory of Virology of Wuhan University, influenza virus can significantly promote the infection of the new coronavirus, which increases the infectivity of the new coronavirus and leads to more serious diseases, such as more serious lung pathological damage and higher new coronavirus load. quantity.


The new variants of Omicron BA.2.12.1, BA.4 and BA.5 make the previously established immune barrier face great challenges. Australia just experienced a COVID-19 pandemic caused by the original strain of the COVID-19 Omicron in January 2022, with a cumulative infection of more than 4 million people and a cumulative death of more than 5,800 people.

In terms of vaccination, more than 95% of Australians over the age of 16 have received two doses of the COVID-19 vaccine; among those eligible for the booster shot, 67% have completed the vaccination.


However, the reason why BA.2.12.1, BA.4 and BA.5 have attracted much attention lies in the variation of key sites on their spike proteins. The spike protein is the “key” for the new coronavirus to enter human cells. Variations in the spike protein may affect viral transmission and immune evasion.


The L452 site on the spike protein of BA.2.12.1, BA.4 and BA.5 was mutated. L452 is the key mutation site of the Delta mutant strain. L452 gives Delta the advantage of transmission and immune escape, while the original Omicron strain does not have this mutation.


According to the current preliminary research, BA.2.12.1, BA.4 and BA.5 have more than 25% propagation advantage over BA.2. At the same time, a stronger immune escape capability means there will be more breakthrough infections.


The latest research by Xie Xiaoliang’s team at Peking University shows that BA.2.12.1 and BA.4/BA.5 have the strongest ability to escape humoral immunity.

Of particular note, compared to BA.2, BA.2.12.1 and BA.4/BA.5 showed stronger sera from subjects vaccinated with three doses of vaccine and then infected with Omicron BA.1 neutralization escape.


At present, BA.4 and BA.5 have caused the fifth wave of the epidemic in South Africa. And BA.2.12.1 pushed the COVID-19 epidemic in the United States to resume its upward trend.

According to the CDC, there is some early evidence in the United States that BA.2.12.1 is spreading faster than the Omicron variant. Omicron is considered to be the most contagious new coronavirus variant strain to date, and BA.2.12.1 is the fastest spreading among the many Omicron sub-variants.

BA.2.12.1 is the next generation of the BA.2 mutant strain. BA.2 spreads at least 30% higher than BA.1. According to CNN, the transmission power of BA.2.12.1 is estimated to be 23% to 27% higher than that of its predecessor, BA.2.


According to the latest surveillance data from the CDC of the US Centers for Disease Control and Prevention, the BA.2.12.1 variant has accounted for 61.9% of New York and New Jersey.

In the United States, the BA.2.12.1 variant has also accounted for 36.5%, which is a 29.4% surge from the previous 28.2%.






BA.2.12.1 BA.4 and BA.5 All appear in Australia: 2nd highest infection rate in the world.

(source:internet, reference only)

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