China has seen six deaths due to a novel strain of influenza that can infect birds and humans. So far human to human spread hasn’t been documented. What if this strain crosses the species barrier? Imagine a virus capable of killing over 90% of the people it infects that also can spread as rapidly as cruise ship diarrhea.

http://www.reuters.com/article/2013/04/05/us-usa-birdflu-cdc-idUSBRE9340SY20130405