Dr. Michael Chan Chi-wai, Associate Professor of School of Public Health and Principal Investigator, Centre for Immunology and Infection (C2i), Hong Kong Science and Technology Park (HKSTP) and Professor John Nicholls, Professor of Department of Pathology, HKUMed have pioneered the use of ex vivo cultures of the respiratory tract for investigating many emerging virus infections since 2007, such as avian influenza, coronavirus of the Middle East Respiratory Syndrome (MERS). Now this technique has been applied to understand why the omicron variant may differ in transmission and disease severity from other SARS-CoV-2 variants.

This method uses lung tissue removed for treatment of the lung, which is normally discarded, for investigating virus diseases of the respiratory tract. Dr. Chan and his team successfully isolated the omicron SARS-CoV-2 variant and used this experimental model to compare infection with the original SARS-CoV-2 from 2020, the delta variant and the recent omicron variant. They found that the novel omicron variant replicates faster than the original SARS-CoV-2 virus and delta variant in the human bronchus. At 24 hours after infection, the omicron variant replicated around 70 times higher than the delta variant and the original SARS-CoV-2 virus. In contrast, the omicron variant replicated less efficiently (more than 10 times lower) in the human lung tissue than the original SARS-CoV-2 virus, which may suggest lower severity of disease.