The fatality rate depends on which form of H5N1 virus you have been exposed to. There is one form of the virus that has a 'death rate' of only about 25% - 30%. That form of the virus is spreading like wild fire in Asia. Another from of the virus kills about 90%. Remember the 1918 Spanish Flu killed about 50 million people worldwide. The death rate from that pandemic was only about 5%
Read reports here The really bad thing about the Spanish Flu was it killed very healthy people in only about 24 hours. There are anecdotal reports about people getting on trolley in NY and going to work. Many were found dead on the trolley later when they returned home. The Spanish Flu was also spread around the world by migrating birds.
The H5N1 virus kills very healthy people too. Use your imagination. 'Nuff said.