If an outbreak were to occur in the West, while the threat would be high and mortality figures could rise into the tens of thousands, however, most Western nations have antibiotics and treatments for biological threats and eventually bring the outbreak under control. But what happens if by mistake or by an act of terror these biological infections invade countries that do not have medication or treatment?
If a powerful biological weapon were to be used against the United States or some other Western nation, theoretically within 48 hours most of the world's countries could begin to register outbreaks themselves. Since many of the nations in Africa and Asia do not have the medications needed, and with the Western nations dealing with their own outbreaks holding on to their supplies, in theory at least billions of people in those nations could die. The irony here is that the Muslim fundamentalists may actually kill most of the world's Muslim population, and that is perhaps why smallpox or some other easily spread biological agent has not been used against the US or any other Western nation.
Anthrax is not easily spread, and while deadly it is unlikely that even with a large outbreak in the US could the threat be spread to the Middle-east, Southeast Asia and Africa, where most Muslims live.