Scientists from Hong Kong report new findings that support the hypothesis that some H5N1 avian influenza viruses are particularly deadly to humans because they can trigger a “cytokine storm” that causes the immune system to overreact (Zhou J et al. J Infect Dis. 2006;194:61-70).
The researchers infected cultured human immune cells (monocyte-derived macrophages [MDMs]) with human influenza virus or with the H5N1 strain that caused a deadly 1997 outbreak in Hong Kong. They found that the H5N1-infected MDMs produced much higher levels of chemokines, a type of cytokine that directs white blood cells to inflammation sites. In addition, levels of chemokines and chemokine receptors were higher in MDMs from adults than in MDMs from newborns, suggesting that chemokines might be a key to the 1997 outbreak's higher mortality rate among adults.
Stephenson J. Avian Flu Clue. JAMA. 2006;296(3):272. doi:10.1001/jama.296.3.272-d