Study points to Omicron’s higher transmissibility, but lower severity

RIO DE JANEIRO, BRAZIL – A study from the University of Hong Kong Medical School (HKUMed) analyzed the Omicron variant’s ability to replicate and pointed out that it may indeed be more transmissible, yet cause less severe infectious conditions. The researchers pointed out that despite its reduced severity, the strain’s overall risk is “probably very significant.”

To reach their findings, scientists used lung tissue to analyze how the original strain of the novel coronavirus, the Delta, and the Omicron infect the human respiratory tract. The research is still undergoing peer review before being published in a scientific journal, the educational institution said.

The research found that when compared to the other two strains, the Omicron multiplies 70 times faster in human bronchi (tube-shaped structures that connect the trachea and lungs, whose function is to route air to these organs). This may explain why the strain detected in South Africa is more transmissible – as shown by preliminary findings cited by the World Health Organization (WHO).

In lung tissue, formed by the alveoli (responsible for the gas exchange that carries oxygen to the blood), the replication of the new variant seems to be less efficient, an indication that the disease it causes may be less severe. The Omicron multiplies about 10 times slower than the Delta and the original variant, the study pointed out.

In severe Covid conditions, the virus mainly attacks the alveoli. Inflammation of these “air sacs” fills them with fluid, which impairs gas exchange. Thus, the blood cannot receive the proper amount of oxygen or eliminate carbon dioxide, causing shortness of breath.

Research leader Michael Chan Chi-wai pointed out in a statement that the severity of a disease is not only determined by the virus’ ability to replicate, but also depends on the patient’s immune response. “By infecting many more people, an infectious virus can cause more severe disease and death, despite the virus being less pathogenic,” he warned.

Chi-wai also cited that recent studies by his teams have shown that “the Omicron variant can partially escape the immunity provided by vaccines and previous infections.” Therefore, he assesses that the global threat of the new strain is “probably very significant.”

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