Reply #2: It's not bacterial pneumonia

[targetpractice]

The secondary pneumonia is due to fluid leaking into the lungs because of an uncontrolled immune response to the H1N1 virus. An overly-aggressive immune response in healthy people can cause "cytokine storm" resulting in damage to the lung tissue.

You can read more about it here... http://en.wikipedia.org/wiki/Cytokine_storm

Unfortunately, the robust immune systems of 20-40 year olds may be a liability. This may explain why young adults are showing up in Mexico City hospitals. Mexican children may be experiencing mild cases (like in the US) and are not reporting to the hospitals... therefore they are not being counted. Most of the US cases are in children.