Bird flu found to spread rapidly in lung tissue

H5N1 flu is found by researchers to spread quickly in the lungs, which is why the disease is so lethal. Sixty percent of victims succumb to respiratory distress syndrome because the bird flu virus targets human pulmonary endothelial cells and destroys them from a profound inflammatory immune response.

Endothelial cells are essential for the lungs to function, explains study coauthor Terrence Tumpey of the Centers for Disease Control and Prevention.

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Compared to the seasonal influenza virus, H5N1, or bird flu, produces an overwhelming release of immune system chemicals called cytokines in the lungs which creates an inflammatory response that leads to death of pulmonary endothelial cells.

Tumpey says the complete mechanism of how H5N1 kills isn’t entirely known.

"The research team found, but identified one virulent factor, the cleavage site of the viral surface glycoprotein hemagglutinin, which we found to be critical for the production of infectious progeny H5N1 virus in pulmonary endothelial cells," Tumpey said, though other factors that make bird flu especially dangerous may still be unknown."

Tumpey also explains it may be possible to halt lung damage from the virus with anti-inflammatory medications.Targeted therapies, combined with anti-viral drugs is suggested as a possible treatment approach by the authors.

The new study identifies how H5N1 bird flu attacks the lungs to lead to respiratory distress. The authors note the mechanism of lung injury is similar to the Spanish influenza pandemic of 1918, but mortality rates, though high, was far less than that seen with H5N1.

J. Virol. 86:667-678
"Human pulmonary microvascular endothelial cells support productive replication of highly pathogenic avian influenza viruses: possible involvement in the pathogenesis of human H5N1 virus infection."
Hui Zeng, et al.
January, 2012

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