25 Apr 2013

The collaborative research team from The University of Hong Kong (HKU) and Zhejiang University has made a breakthrough in understanding the human infections with avian influenza A H7N9 virus. They analyse four Zhejiang infected patients and discover for the first time that the patient’s virus is genetically very closely related (>/=99.4%) to the chicken virus isolated from the epidemiologically linked poultry market. The researchers believe that poultry wet market might be the source of virus. The research data is published online today (25 April) in the leading international medical journal The Lancet.

The Lancet publishes the research entitled “Human infections with the emerging avian influenza A H7N9 virus from wet market poultry: clinical analysis and characterisation of viral genome” in a timely manner. The research analyses four epidemiologically unlinked Zhejiang patients suffering from severe acute community acquired pneumonia not responding to typical and atypical antimicrobial coverage who are found to have the H7N9 virus. The team shows for the first time that the patient’s virus is genetically very closely related (>/=99.4%) to the chicken virus isolated from the epidemiologically linked poultry market. Indeed about 20% of the chickens in the epidemiologically linked markets were infected with this virus. The researchers thereby believe that poultry wet market might be the source of virus of avian influenza A H7N9 human infection.

Moreover, the team conducts a characterisation of viral genome. They find that the patient virus has a PB2 Asp701Asn mutation which is important for adaptation to mammalian host. There are also important mutations on the haemagglutinin, a virus surface protein, facilitating the virus attaching to mammalian host cell. These include the HA Gly186Val and Gln226Leu. But no person-to-person transmission was found in 303 household or workplace contacts and 82 health-care workers with unprotected exposure to the four patients.

Among these four patients, two of them died with respiratory failure, multiorgan dysfunction and markedly elevated serum cytokines and chemokines when compared with the survivors. Research found fatal but not the mild cases exhibit aberrant proinflammatory response of "cytokine storms", which resembles that observed in H5N1 or SARS patients.

Another important finding is that virus testing appeared to be more sensitive with lower respiratory tract specimens such as sputum than throat swabs.

All in all, further studies on the virus evolution and disease pathogenesis will be performed to improve disease management and epidemic control.

About the research team

The research team is led by Professor Li Lanjuan of Zhejiang University and Professor Yuen Kwok-yung, the Co-director of the State Key Laboratory of Emerging Infectious Diseases, Department of Microbiology of The University of Hong Kong Li Ka Shing Faculty of Medicine. Team members of HKU also include Dr Chen Honglin, Associate Professor, Dr Kelvin To Kai-wang, Clinical Assistant Professor, and Dr Jasper Chan Fuk-woo, Clinical Assistant Professor of Department of Microbiology. A multidisciplinary collaboration between HKU and Zhejiang University has made the new discovery in understanding the human infections with avian influenza A H7N9 virus.