Avian influenza H5N1 virus not only affects the respiratory system but gastrointestinal tract, immune and central nervous systems also, and it can be transmitted from mother to foetus through placenta, say researchers.
The findings published in the journal Lancet are based on a collaborative study by researchers from Beijing University, Columbia University Mailman School of Public Health and SUNY Downstate, which sheds light on the anatomic distribution of the virus and its pathogenesis.
Initially, the virus seemed to be limited to the lungs, but later reports have suggested that influenza A H5N1 could spread beyond the lungs. Lung damage is severe and disproportionate to the number of cells that are infected, with macrophages and T-cells targeted for infection.
The new study suggests that lung damage is not due to virus replication alone, and supports the theory that indirect effects, such as soluble factors known as cytokine and chemokines, are important, say the researchers.
According to them, the newly obtained data are important in the clinical, pathological, and epidemiological investigations of human H5N1 infection.
The researchers say that the findings also have widespread implications for public health and healthcare providers, because though there has been considerable progress in developing surveillance networks, diagnostic tests, drugs and vaccines, scientists have to date achieved limited information about the mechanisms by which H5N1 causes disease.
"The work helps us to understand H5N1's high fatality rate, as well as serving as model for global collaboration in the field of emerging infectious diseases," said the study's senior author Dr. W. Ian Lipkin, director of the Centre for Infection and Immunity at Columbia University Mailman School of Public Health and professor of Epidemiology, Neurology, and Pathology at Columbia.