01 Feb 2010

Researchers at the Departments of Microbiology and Pathology from The University of Hong Kong published a research on the pandemic H1N1 virus. Researchers compared the ability of the pandemic H1N1 virus, the seasonal H1N1 and H3N2 influenza viruses to replicate in cells and tissue samples from the human upper and lower respiratory tract and the conjunctiva (the cells lining the surface of the eye). It was found that the pandemic H1N1 virus is more efficient than seasonal influenza H1N1 or H3N2 viruses in infecting the conjunctival surfaces of the eye, apart from infecting humans via the respiratory tract. This research was published in a publication in the prestigious scientific publication, American Journal of Pathology.

Research findings

Cells of the respiratory tract are the main targets of influenza viruses. Using novel methods for culture of human respiratory and conjunctival cells and tissues, they found that the pandemic H1N1 and seasonal H1N1 viruses have comparable efficiency in replicating in the upper respiratory tract. However, at 33oC, the H1N1 pandemic virus replicates to higher levels in the respiratory airways (bronchus). They also found that when human respiratory epithelial cells were infected with the pandemic H1N1 virus and seasonal H1N1 virus, unlike the avian influenza H5N1 virus, the pandemic H1N1 virus did not lead to a hyper-activation of the human cell cytokine response, a mechanism believed to contribute to the disease severity of avian H5N1 virus infection in humans. This finding supports the clinical observation that the pandemic H1N1 in the vast majority of individuals does not cause severe cytokine related human illness comparable to that caused by infection with avian H5N1 influenza.

The investigators also found that the pandemic H1N1 virus is more efficient than seasonal influenza H1N1 or H3N2 viruses in infecting the conjunctival surfaces of the eye, suggesting that the H1N1 pandemic virus differs from seasonal influenza viruses in the type of receptors it uses to infect human cells. The findings suggest that, the eyes may be one important route of infection of humans. To reduce transmission of H1N1 pandemic in the community, one should wash hands frequently and before touching the eyes and nose.

Overall, the findings from the HKU researchers indicate that the pandemic H1N1 virus differs from seasonal influenza viruses in subtle ways and these differences may explain why the pattern of illness it causes is not identical to that caused by seasonal influenza.

This research was led by Dr Michael Chan Chi-wai and Professor Malik Peiris at the Department of Microbiology. The research team included Dr Renee Chan Wan-yi and Dr John Nichollos at The Department of Pathology, and other researchers from the Eye Institute, Departments of Clinical Oncology and Anatomy at The University of Hong Kong, and the Department of Cardiothoracic Surgery of the Queen Mary Hospital.