Why is H1N1 virus fatal, study finds

Scientists have found high levels of the molecule called Interleukin 17 (IL-17) in the blood of those infected with H1N1. This molecule may be causing the damage to the lungs and proving fatal.

According to the researchers, the molecule IL-17 controls the action of the white cells that regulate the immune system of the body, enabling it to fight bacterial and viral infections.

However, if the molecule goes "out of control", it can cause inflammatory autoimmune diseases such as rheumatoid arthritis and asthma.

Dr. David Kelvin, head of the Experimental Therapeutics Division at the Toronto General Hospital Research Institute, one of the leaders of the study stated, "Most people have a well-balanced and controlled response to H1N1 infection. But, in rare cases, individuals have what we think is an uncontrolled immune response. We think that the high levels of IL-17 is at the centre of this uncontrolled response."

Study analyzes different levels of IL-17
Researchers from the Hospital Clinico Universitario de Valladolid in Spain and the University Health Network conducted a study to analyze different levels of the regulating molecule IL-17 during the initial wave of the pandemic in July.

They enrolled a total of 50 persons in 10 hospitals in Spain. The study involved 20 hospitalized patients in intensive care, 15 outpatients suffering from mild H1N1 influenza and 15 healthy subjects who served as controls.

Observations by the researchers
The researchers found that the severely infected patients had elevated levels of molecule in their blood which may be responsible for the inflammation of the lungs. On the other hand, patients with a milder form of the disease had lower levels of it.

"In rare cases, the virus causes lung infections requiring patients to be treated in hospital. By targeting or blocking TH17 in the future, we could potentially reduce the amount of inflammation in the lungs and speed up recovery," says Dr. David Kelvin.

The experts conceded that the research was still in the early stages and required further studies. However, they believe the test could be beneficial in detecting high levels of IL-17 which could lead to preventive therapies for a quick recovery in severely infected swine flu patients.

Dr. Kelvin stated, "A diagnostic test could let us know early who is at risk for the severe form of this illness quickly.”

The research titled, "Th1 and Th17 hypercytokinemia as early host response signature in severe pandemic influenza" is published in the December issue of the Journal of Critical Care.