The H1N1 flu outbreak that began in
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, which are signaling chemicals that help mobilize immune cells capable of removing infectious agents from the body. When too many cytokines are produced, they can stimulate an inflammatory response in which the accumulation of immune cells and fluid at the site of infection may prevent affected tissues and organs such as the lungs from functioning properly and may even cause death.
H5N1 avian influenza virus—parts of which are present in the Mexican H1N1 swine flu virus causing the current outbreak—tend to cause an unusually high proportion of deaths among healthy young adults with well-functioning immune systems who become infected, most likely due to this cytokine storm phenomenon. The Spanish influenza pandemic of 1918, for example, was particularly deadly for young healthy adults.
David L. Woodland, PhD, editor-in-chief of Viral Immunology, and president and director of the Trudeau Institute, Inc. of
What we do know, he adds, 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.