[muawiyah]

Insofar as we have been let to know (publicly) by the FBI or others, all the anthrax is the same. Earlier there was suspicion that we had independently operating "look alike" attackers.

The big dividing line among the people who developed symptoms of infection is a simple one. All the deaths occurred with people over 50.

This group of people has substantial ethnic diversity. It could be that some populations have a degree of inherited immunity.

[Mitchell]

Insofar as we have been let to know (publicly) by the FBI or others, all the anthrax is the same.

My understanding is that this is not true. All the anthrax is of the same strain (Ames), but there are small genetic differences. There also appear to be differences in physical preparation ("weaponization").

[Mitchell]

The big dividing line among the people who developed symptoms of infection is a simple one. All the deaths occurred with people over 50.

But Blanco was 74 -- not only did he survive, but he is the only survivor to have fully recovered.

In any case, I'm not suggesting a difference in mortality rate, but a possible difference in long-term effects among the survivors. (This is speculative, since there aren't enough cases for the difference to be statistically significant all by itself. But this adds to the other evidence that there were at least two, and maybe three, batches of anthrax involved.)