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.