Do not underestimate anthrax just because the initial use was in warning form. It could just as easily have been widely distributed and killed thousands. Whoever sent it has not been caught, and most certainly did not use up their supply. In other words, they can attack again, whenever they feel like it.
They definitely know more than they are letting on for the sake of avoiding panic.
You can say that again.
BTW: Smallpox is contagious and could kill many more people, but its use as a weapon is more difficult. That is because the attackers would have trouble protecting their own nations as the disease spread. That is why anthrax is cited as a military threat much more often than smallpox.
If you really want to worry, consider the danger if camelpox could be genetically engineered to be a human threat. The arabs believe they would be immune because of their exposure to camels, while we would not.
By no means did I intend to underestimate the widespread damage anthrax could cause. It's just a lot more difficult to disperse and we do have cipro. Unlike anthrax, smallpox (or indeed cowpox) is contagious and could be spread by a couple of suicide bioterrorists coast to coast.