Image Source: ksjtracker.mit.edu
Flu in general is characterized by cold like symptoms plus body and head aches. It is a benign and self-limiting illness that subsides after two to seven days. A small percentage of patients mostly the very young, the elderly and those who are debilitated however develop life-threatening complications like pneumonia. The number of deaths during an epidemic could be staggering, although the fatality rate of flu is low.
On the other hand, bird flu or avian flu is also caused by the influenza type A virus. The strains of virus that produce it are different from those that cause human flu. It is primarily a disease of birds but sometimes it mutates and infects humans too. The currently available human flu vaccine cannot prevent bird flu because it was meant only for the strains of human influenza. It can only reduce the incidence of human flu thus, prevent the genetic re-assortment among the different strains of the virus and the occurrence it.