Scientists are suggesting that the swine flu virus may be more dangerous for healthy young adults because it likely kills its victims by inducing a "cytokine storm", in which a patient's hyper-activated immune system causes potentially fatal damage to the lungs.
Cytokines are signalling chemicals that help mobilize immune cells capable of removing infectious agents from the body.
Research studies and review articles published in the journal Viral Immunology reveal that a cytokine storm occurs when the body's immune system over-reacts to an intruder, such as a virus, by producing high levels of cytokines.
The reports further suggest that too much production of cytokines can stimulate an inflammatory response in which the accumulation of immune cells and fluid at the site of infection may prevent affected organs, such as the lung, from functioning properly, and may even cause death.
The researchers behind these articles say that the swine flu contains genetic components of the H5N1 avian influenza virus, which tend to cause an unusually high proportion of deaths among healthy young adults, most likely due to the overproduction of cytokines.
Dr. David L. Woodland, Editor-in Chief of Viral Immunology, emphasizes that much is still not known about the current influenza outbreak and the human/avian combination virus causing it.
"We do not know how long ago this virus emerged, how deadly it is, whether it has pandemic potential, how the severity of infection relates to patient age, and why some infected patients die-whether a cytokine storm is responsible for these deaths," he says.
He further says what scientists know is that some H1N1 viruses have pandemic potential, and that historical evidence supports the possibility that young healthy adults may be especially susceptible to more severe infection and poor outcomes due to the ability of a strong immune system to initiate a cytokine storm.