http://http://www.biologynews.net/archives/2009/12/15/first_immunological_clue_to_why_some_h1n1_patients_get_very_ill_or_die.html

An International team of Canadian and Spanish scientists have found the first potential immunological clue of why some people develop severe pneumonia when infected by the pandemic H1N1 virus.

Researchers from the Hospital Clinico Universitario de Valladolid in Spain and the University Health Network found high levels of a molecule called interleukin 17 in the blood of severe H1N1 patients, and low levels in patients with the mild form of the disease.

Interleukin 17 is typically produced by the body to fight disease, however ther are times when it becomes "out of control" and is more harmful than helpful. interleukin 17 can cause paitients to have inflamation of the lungs which leads them to have to be hospitalized. Researchers believe that they can decrease the number of hospitalizations if the can control the interleukin 17.

"A diagnostic test could let us know early who is at risk for the severe form of this illness quickly," he said, adding that high levels would indicate a failure of the immune system to eliminate the virus, similar to what happened during the 1918 Spanish flu when huge numbers of deaths occurred due to a deadly influenza A virus strain of subtype H1N1.