An international study has found a molecule in H1N1, or swine flu, patients whose levels determine the severity of the illness or even death.

Canadian and Spanish scientists have found this molecule called Interleukin 17 (IL-17) to be the first potential immunological clue of why some people develop severe pneumonia when infected by the H1N1 virus. The study was carried in 10 Spanish hospitals during the first pandemic wave in July and August this year.

They found high levels of IL-17 molecule in the blood of severe H1N1 patients and low levels in patients with the mild form of the disease. But in certain circumstances, the molecule becomes out of control, leading to inflammation and autoimmune diseases like H1N1.

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

"In rare cases, the virus (molecule) 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,'' Canadian professor David Kelvin, who was part of the research team, said.

Kelvin said the clinical applications of their study will take some time. But a test to determine who has high levels of this molecule is possible in the near future, he said. "A diagnostic test could let us know early who is at risk for the severe form of this illness quickly,'' the Canadian said.

The high levels of the molecule would indicate a failure of the immune system to eliminate the virus, similar to what happened during the 1918 Spanish flu when a deadly influenza A virus strain of sub-type H1N1 ravaged populations, he added.

The statement also quoted Dr Jesus Bermejo-Martin of the Spanish team as saying that identifying drugs that regulate the activity of IL-17 may provide alternative treatments for patients with severe H1N1.