“A cytokine storm is a potentially fatal immune reaction consisting of a positive feedback loop between cytokines and immune cells, with highly elevated levels of various cytokines.”
“When the immune system is fighting pathogens, cytokines signal immune cells such as T-cells and macrophages to travel to the site of infection. In addition, cytokines activate those cells, stimulating them to produce more cytokines. Normally this feedback loop is kept in check by the body. However, in some instances, the reaction becomes uncontrolled, and too many immune cells are activated in a single place. The precise reason for this is not entirely understood, but may be caused by an exaggerated response when the immune system encounters a new and highly pathogenic invader. Cytokine storms have potential to do significant damage to body tissues and organs. If a cytokine storm occurs in the lungs, for example, fluids and immune cells such as macrophages may accumulate and eventually block off the airways, potentially resulting in death.”
“t is believed that cytokine storms were responsible for many of the deaths during the 1918 influenza pandemic, which killed a disproportionate number of young adults (a phenomenon that could repeat itself in future flu pandemics). In this case, a healthy immune system may have been a liability rather than an asset. Preliminary research results from Hong Kong also indicated this as the probable reason of many deaths during the SARS epidemic in 2003. Human deaths from the bird flu H5N1 usually involve cytokine storms.”
The 1918 pandemic killed more people than WW1 and actually went around the world in three incarnations. This was why the bird flu was cause for so much concern. Ground zero was Fort Riley Kansas, 100 miles north of Wichita Kansas (where I live). It is suspected that a pig was the vector.