Causes

Anthrax spores are formed by anthrax bacteria that occur naturally in soil in most parts of the world. The spores can remain dormant for years until they find their way into a host. Common hosts for anthrax include wild or domestic livestock, such as sheep, cattle, horses and goats.

Although rare in the United States, anthrax is still common throughout the developing world, in places such as Central America and South America, sub-Saharan Africa, Central Asia and southwestern Asia, southern Europe and Eastern Europe, and the Caribbean.

Most human cases of anthrax occur as a result of exposure to infected animals or their meat or hides. In the United States, a few people have developed anthrax while making traditional African drums from the skins of infected animals.

One of the few known instances of nonanimal transmission was a bioterrorism attack that occurred in the United States in 2001. Twenty-two people developed anthrax after being exposed to spores sent through the mail, and five of those infected died.

More recently, in two separate outbreaks, heroin users in Europe contracted anthrax through injecting illegal drugs. A total of 40 people died. Heroin sold in Europe likely comes from areas where naturally occurring anthrax is more common.