Of course we should be concerned. I was merely pointing out that a random mutation does not have a 50% chance of making the disease more deadly to humans. I don’t know what the numbers are, but the chance is a great deal lower than that. The reason pandemics are rare is that only an occasional mutation is able to easily infect people.
Flu is a poor choice for a bio-weapon, since it mutates so readily. You could come up with a highly efficient killer and it promptly mutates to relative harmlessness when released.
An efficient bio-weapon would lock in the deadly characteristics. There are a great many other organisms that are more likely as a basis for such a weapon.
But, because influenza is airborne it spreads more efficiently, i.e., it is highly contagious. Also, the terrorists (man-made disaster agents) could vaccinate their people before hand. Just thinking....