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Eyes an ‘important route’ for coronavirus transmission

Public health researchers believe the eye may be a key entry point for coronavirus to infect the body, in a world-first study that reveals the current strain is up to 100 times more infectious than SARS.

New testing data published in The Lancet Respiratory Medicine this month has demonstrated that SARS-Cov-2 – the strain of coronavirus that causes COVID-19 disease – infected the upper respiratory airways and conjunctiva much more efficiently than the 2003 SARS-CoV (SARS).

The researchers from the School of Public Health, LKS Faculty of Medicine of the University of Hong Kong (HKUMed), claim they are the first in the world to provide evidence that coronavirus can infect through both facial entry points.

More reading: Study findings suggest coronavirus replicates in the eye

In this study, co-author Dr Michael Chan Chi-wai, associate professor of the School of Public Health, HKUMed, and his research team compared the infection of SARS-CoV-2, SARS-CoV and the influenza viruses H5N1 (bird flu) and H1N1pdm2009 (swine flu) using human upper respiratory tract and eye tissues.

“We found that SARS-Cov-2 is much more efficient in infecting the human conjunctiva, the cells lining the surfaces of the eyes,  and the upper respiratory airways than Sars, with virus level some 80 to 100 times higher,” Chan said told the South China Morning Post, adding that its level of infection is comparable to that observed with swine flu.

The HKUMed research team (from left to right) Professor Malik Peiris; Tam Wah-Ching, professor in medical science and chair professor of virology, School of Public Health; Professor John Nicholls, clinical professor, Department of Pathology; Dr Michael Chan Chi-wai, associate professor, School of Public Health; and Dr Kenrie Hui Pui-yan, research assistant professor, School of Public Health. Image: HKUMed

“This explains the higher transmissibility of COVID-19 than that of Sars. This study also highlights the fact that eyes may be an important route of SARS-CoV-2 human infection.”

Taken together, the researchers say this explains the higher transmissibility of the novel pandemic SARS-CoV-2 than that of SARS-CoV.

In a previous study, the research team discovered that SARS-CoV-2 can remain alive for several days on smooth surfaces such as stainless steel, glass and plastic.

The latest findings highlight the possibility that infectious virus can be spread from such contaminated surfaces by hands, when a person touches the surfaces and rubs their eyes afterwards.

This, the researchers state, demonstrates why it is vital to avoid touching the eyes when in public areas, and the importance of regular hand washing to prevent accidental transfer of SARS-CoV-2 from contaminated surfaces to human eyes and noses.

“There is a need for studies like those done by this research team, which are inclusive of diverse viruses previously associated with human pandemics, and viruses believed to have the potential to do so, that use a range of relevant respiratory and non-respiratory tissue and cell types that might support virus replication following multiple exposure routes,” Dr Jessica Belser, an epidemiological expert from the National Center for Immunization and Respiratory Diseases (NCIRD), the Centers for Disease Control and Prevention (CDC), said.

“These laboratory studies provide crucial context for interpretation of what makes each virus unique and how best to develop medical countermeasures to improve human health.”

This image shows the coronavirus and influenza virus infected cells (in red colour) in human bronchus, lung and conjunctiva in explants culture. Image: HKUMed