H1N1 infects lungs far deeper than seasonal virus

Get ready for influenzas possible second strike in winter: WHO

This may explain why people infected with H1N1 influenza are more likely to suffer more severe symptoms than those infected with seasonal flu, says a research conducted in Nature Biotechnology.

The discovery increases the scientist’s anxiety level.

If H1N1 virus returns in winter in a mutated form infecting the lungs, it would lead to a far more serious pandemic than the ongoing one.

The World Health Organisation has asked its member countries in south east Asia to be on the guard for H1N1’s possible second strike in the winter. The warning was issued at a regional meeting at Kathmandu on Wednesday. Influenza viruses infect cells by attaching to bead-like molecules called receptors on the surface of the cell. Different viruses attach to different receptors and if a virus cannot find its specific receptors, it cannot get into the cell.

Seasonal influenza viruses attach to receptors found on cells in the nose, throat and upper airway, enabling them to infect a person’s respiratory tract.

Carried out by scientists at the Imperial College, London, the new study illustrates how H1N1 virus can attach to a receptor found on cells deep inside the lungs, resulting in a more severe lung infection. This is something seasonal flu cannot do. The pandemic influenza virus’s ability to stick to the additional receptors may explain why the virus replicates and spreads between cells more quickly. If a flu virus binds to more than one type of receptor, it can attach itself to a larger area of the respiratory tract, infecting more cells and causing a more serious infection.

While by and large people affected by H1N1 worldwide had mild symptoms, some of the infected persons had serious lung infections. The new research shows why.

The researchers found that pandemic H1N1 influenza bound weakly to the receptors in the lungs than to those in the upper respiratory tract, which explains why a bulk of the infected people experienced mild symptoms. But they are concerned as the H1N1 virus has potential to mutate for binding more strongly to these lung receptors in future.

“If the flu virus mutates in the future, it may attach to the receptors deep inside the lungs more strongly. This could mean that more people would experience serious symptoms,” said Ten Feizi, one of the project scientists from the Imperial College.