Being young and healthy ... can suck!

From time to time, viruses evolve that seem to kill a disproportionate number of the young and healthy. In certain cases  like the “Spanish Flu of 1918”, the SARS outbreak in Hong Kong, and the recent bird flu pandemics, a healthy immune system may have been a liability rather than an asset. Intuitively, this does not make sense.  Why would a healthy person be at greater risk? Well, I am glad you asked!

Have you ever heard of a cytokine storm?

When the body identifies a pathogen, an immune response ensues. Part of the immune system communication is a small cell-signaling protein molecule called cytokine, which tells immune cells like macrophages and T-cells to travel to the site of the infection. Cytokines also activates other immune cells, stimulating them to produce more cytokines in a process called a positive feedback loop.  Normally, this feedback loop is kept under control by some processes I do not understand; however, sometimes, the reaction becomes uncontrolled. This is known as a cytokine storm.

In other words, a cytokine storm causes an exaggerated immune response that can kill a person. The precise reason for this is not entirely understood but it is believed that this is the reason why a new and highly pathogenic invader causes higher fatality rates among young, healthy people with good immune systems.

How about … never mind, that sucks!