Swine Flu Burrows Into Lungs: Study

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THURSDAY, Sept. 10 (HealthDay News) -- New British research confirms previous reports that the H1N1 swine flu goes deeper into the lungs than ordinary seasonal flu, possibly explaining why it's often more severe in some people.

"Most people infected with swine-origin flu in the current pandemic have experienced relatively mild symptoms," Ten Feizi, a professor at Imperial College London and co-author of a study released Thursday, said in a college news release. "However, some people have had more severe lung infections, which can be worse than those caused by seasonal flu. Our new research shows how the virus does this -- by attaching to receptors mostly found on cells deep in the lungs. This is something seasonal flu cannot do."

The finding echoes that of another study, published earlier this month in PLoS Currents. That work, from University of Maryland researchers, found that H1N1 reached deeper into the lungs of ferrets when compared to seasonal flu strains.

According to the researchers behind the new study, flu viruses infect the body by attaching themselves to receptors on the outside of cells. This allows the viruses to hijack the cells and infect even more cells, a cycle that can lead to illness and death.

The new study, published Sept. 10 in the journal Nature Biotechnology, finds that swine flu attacks cells deep in the lungs, whereas seasonal flu targets cells in the nose, throat and upper airway.

The researchers suspect this may explain why swine flu can be so much more serious than seasonal flu: It may simply be able to attack more cells.

The study also found that the swine flu virus binds more weakly when it goes after cells deeper in the lungs versus cells higher up in the respiratory system. However, "if the flu virus mutates in the future, it may attach to the receptors deep inside the lungs more strongly, and this could mean that more people would experience serious symptoms. We think scientists should be on the lookout for these kinds of changes in the virus so we can try to find ways of minimizing the impact of such changes," Feizi said.

-- Randy Dotinga

SOURCE: Imperial College London, news release, Sept. 10, 2009

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