H5N1 'more invasive than thought'
[BEIJING] The post mortems of two people who died after H5N1 infection have revealed that the virus infects more human organs than previously thought.
The study was published in The Lancet last week (28 September).
Lead author Gu Jiang, a professor at the School of Basic Medical Sciences of the Beijing-based Peking University, and colleagues studied post-mortem tissues of one man and one pregnant woman, and also tested the foetus of the woman.
They detected the bird flu virus genetic material and antigens in the lungs, cells of the trachea and the lymph nodes, neurons in the brain and in cells of the placenta.
In the four-month-old foetus, the researchers found both viral genetic material and antigens of H5N1 virus in the lungs, circulating cells of the immune system and in cells of the liver, suggesting the virus can overcome maternal immune protection of the foetus.
As of 10 September, 328 have contracted and 200 people have died from the H5N1 virus, according to the WHO.
Previous studies have indicated the H5N1 could move beyond the lungs but full autopsies of people who have died after H5N1 infection — which would reveal where the virus spreads in the human body — have not been obtained for various reasons, including religious objections.
"The study could change a lot of our previous views," Gu told SciDev.Net.
"For example, the trachea was formerly thought uninfected by H5N1 and this was used to explain that H5N1 could only infect the lower respiratory system, but our studies have clearly shown it is not such a case." (See H5N1 — why it can't spread between people).
The research team also found viral genetic material in the intestinal mucosa, but no viral antigens were found, suggesting the virus does not directly infect intestinal cells. "How they arrive at the place and replicate remains unknown," Gu says.
In an accompanying comment, Wai Fu Ng of Hong Kong's Yan Chai Hospital and Ka Fai To, of Hong Kong's Ki ka Shing Institute of Health Science, say Gu and colleagues' finding of viral parts in the intestinal mucosa could have important implications for infection control because it could represent another route of infection.
But they also suggest that further research should look into how the virus replicates in the organs.
Reference: The Lancet 370, 1137 (2007)
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