Quote: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.[1]

Symptoms
The primary symptoms of a cytokine storm are high fever, swelling and redness, extreme fatigue, and nausea.

Cause
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.[citation needed] 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.[citation needed]

The cytokine storm (hypercytokinemia) is the systemic expression of a healthy and vigorous immune system resulting in the release of more than 150 inflammatory mediators (cytokines, oxygen free radicals, and coagulation factors).[citation needed] Both pro-inflammatory cytokines (such as Tumor necrosis factor-alpha, Interleukin-1, and Interleukin-6) and anti-inflammatory cytokines (such as interleukin 10 and interleukin 1 receptor antagonist) are elevated in the serum of patients experiencing a cytokine storm.[citation needed]

Cytokine storms can occur in a number of infectious and non-infectious diseases including graft versus host disease (GVHD), adult respiratory distress syndrome (ARDS), sepsis, avian influenza, smallpox, and systemic inflammatory response syndrome (SIRS).[2]

The first reference to the term cytokine storm in the published medical literature appears to be by Ferrara et al.[3] in GVHD in February 1993.

Role in pandemic deaths
It 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.[1] 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 for many deaths during the SARS epidemic in 2003.[citation needed] Human deaths from the bird flu H5N1 usually involve cytokine storms as well.[citation needed] Recent reports of high mortality among healthy young adults in the 2009 swine flu outbreak point to cytokine storms as being responsible for these deaths.[4]

Quote:In Mexico, state health authorities looking for the initial source of the outbreak toured a million-pig hog farm in Perote, in Veracruz State. The plant is half-owned by Smithfield Foods, an American company and the world's largest pork producer. Mexico's first known swine flu case, which was later confirmed, was from Perote, according to Health Minister Jos? ?ngel C?rdova. The case involved a 5-year-old boy who recovered.But a spokesman for the plant said the boy was not related to a plant worker, that none of its workers were sick and that its hogs were vaccinated against flu.