Anthrax is an infection that is caused by the bacteria Bacillus anthracis. These bacteria form spores that are hard-shelled, dormant versions of the bacteria. Spores are the form of the bacteria that cause infection. They can survive in the soil for many years.
Anthrax most commonly occurs in animals such as pigs, cattle, horses, and goats, but it can also infect people. Infections in people are caused by contact with the spores through a cut or scratch in the skin (known as cutaneous anthrax), by inhaling the spores (known as inhaled or pulmonary anthrax), or by eating meat that contains the spores (known as intestinal anthrax).
In biological warfare, anthrax can be transmitted intentionally through the air or by contact with an object that has the bacteria on it. Anthrax cannot be passed from one person to another (i.e., it is not contagious).
Symptoms of cutaneous anthrax appear almost immediately, up to one day after infection, whereas pulmonary anthrax symptoms usually appear 2 to 6 days after infection, but may take 6 weeks or longer to show up. Symptoms of intestinal anthrax appear in about 1 to 7 days. The last reported case of anthrax in Canada was in 2001, and it was cutaneous anthrax.
It is very rare that people get anthrax infection through natural causes. However, anthrax can be produced in laboratories and may be used as an agent of biological warfare. Anthrax is used in this manner because of the serious disease that results when the anthrax spores are inhaled. Inhaled anthrax often causes death if it's not treated in the early stages, which is why it is very important to recognize the symptoms of this infection (see "Symptoms and Complications").
The most common type of anthrax infection is cutaneous (on the skin) anthrax. In fact, this accounts for over 95% of naturally-occurring anthrax infections. Cutaneous anthrax infection may take place when someone handles animals or animal products (wool or other woven materials) that are contaminated with anthrax, or if someone handles materials that have been intentionally contaminated with anthrax.
It is quite rare for meat to be contaminated with the bacteria that causes anthrax in North America. Therefore, intestinal anthrax is very rare on this continent.
Inhaled anthrax is by far the most dangerous form of this infection, but also the rarest. It causes symptoms that start out like the flu. These symptoms include fever, chest discomfort, malaise, tiredness, and dry cough. The signs of illness appear as early as 48 hours after the spores of the bacteria have been inhaled.
If the symptoms are not treated quickly, the infection can rapidly turn into a severe infection similar to pneumonia (inflammation of the lungs). Shortness of breath, high fever, fast heart rate, and heavy sweating then develop. Meningitis (swelling of the brain) and pain in the abdomen follow. Few survive more than a few days beyond the development of these types of symptoms. Fortunately, early treatment decreases the risk of death.
Cutaneous anthrax is much less dangerous than the inhaled form of anthrax. When infection occurs in this manner, the skin develops a raised, sometimes itchy bump that looks and feels like an insect or spider bite. Within a day or two, sores develop that usually turn black in the centre. Usually, people with cutaneous anthrax feel only mildly ill. Early antibiotic treatment is almost always successful in curing this type of anthrax.
If cutaneous anthrax is not treated, the bacteria may get into the bloodstream and cause more serious symptoms. Signs of spreading infection include fever, chills, and swollen lymph glands close to the area of the sore.
Intestinal anthrax symptoms include severe abdominal pain, nausea, vomiting, severe diarrhea, fever, and bleeding from the gastrointestinal tract (stomach and intestines).
It is important to remember that anthrax is not passed from person to person. It is very rare for a person to develop anthrax unless the spores get below the surface of the skin or the lining of the stomach or intestines. The inhaled form of anthrax develops only after thousands of spores are inhaled all the way down to the lungs.