Anthrax is a deadly disease caused by Bacillus anthracis, a bacterium that forms spores.

There are three types of anthrax: skin, lung and gastrointestinal.

Anthrax from animals. You can become infected with anthrax by handling products from infected animals or by breathing in anthrax spores from infected animal products (like wool, for example). You can also become infected with gastrointestinal anthrax by eating undercooked meat from infected animals.

Anthrax as a weapon. Anthrax also can be used as a weapon. This happened in the US in 2001. Anthrax was spread by sending letters with powder containing anthrax. This caused 22 cases of anthrax infection, including several deaths.

Inhalational anthrax, mediastinal widening

Anthrax can enter the human body through the intestines (ingestion), lungs (inhalation), or skin (cutaneous) and causes distinct clinical symptoms based on its site of entry. In general, an infected human will be quarantined. However, anthrax does not usually spread from an infected human to a noninfected human. But, if the disease is fatal to the person's body, its mass of anthrax bacilli becomes a potential source of infection to others and special precautions should be used to prevent further contamination. Inhalational anthrax, if left untreated until obvious symptoms occur, may be fatal.

Anthrax can be contracted in laboratory accidents or by handling infected animals or their wool or hides. It has also been used in biological warfare agents and by terrorists to intentionally infect as exemplified by the 2001 anthrax attacks.

Respiratory infection in humans initially presents with cold or flu-like symptoms for several days, followed by severe (and often fatal) respiratory collapse. Historical mortality was 92%, but, when treated early (seen in the 2001 anthrax attacks), observed mortality was 45%.[21]Distinguishing pulmonary anthrax from more common causes of respiratory illness is essential to avoiding delays in diagnosis and thereby improving outcomes. An algorithm for this purpose has been developed.[22] Illness progressing to the fulminant phase has a 97% mortality regardless of treatment.

A lethal infection is reported to result from inhalation of about 10,000-20,000 spores, though this dose varies among host species.[23] As with all diseases, it is presumed that there is a wide variation to susceptibility with evidence that some people may die from much lower exposures; there is little documented evidence to verify the exact or average number of spores needed for infection. Inhalational anthrax is also known as Woolsorters' or Ragpickers' disease as these professions were more susceptible to the disease due to their exposure to infected animal products. Other practices associated with exposure include the slicing up of animal horns for the manufacture of buttons, the handling of hair bristles used for the manufacturing of brushes, and the handling of animal skins. Whether these animal skins came from animals that died of the disease or from animals that had simply laid on ground that had spores on it is unknown. This mode of infection is used as a bioweapon.

Gastrointestinal infection in humans is most often caused by eating anthrax-infected meat and is characterized by serious gastrointestinal difficulty, vomiting of blood, severe diarrhea, acute inflammation of the intestinal tract, and loss of appetite. Some lesions have been found in the intestines and in the mouth and throat. After the bacterium invades the bowel system, it spreads through the bloodstream throughout the body, making even more toxins on the way. Gastrointestinal infections can be treated but usually result in fatality rates of 25% to 60%, depending upon how soon treatment commences.[24] This form of anthrax is the rarest form. In the United States, there is only one official case reported in 1942 by the CDC.[16]

Anthrax skin lesion

Cutaneous (on the skin) anthrax infection in humans shows up as a boil-like skin lesion that eventually forms an ulcer with a black center (eschar). The black eschar often shows up as a large, painless necrotic ulcer (beginning as an irritating and itchy skin lesion or blister that is dark and usually concentrated as a black dot, somewhat resembling bread mold) at the site of infection. In general, cutaneous infections form within the site of spore penetration between 2 and 5 days after exposure. Unlike bruises or most other lesions, cutaneous anthrax infections normally do not cause pain.[24]

Cutaneous anthrax is typically caused when bacillus anthracis spores enter through cuts on the skin. This form of Anthrax is found most commonly when humans handle infected animals and/or animal products (e.g., the hide of an animal used to make drums).

Cutaneous anthrax is rarely fatal if treated,[21] because the infection area is limited to the skin, preventing the Lethal Factor, Edema Factor, and Protective Antigen from entering and destroying a vital organ. Without treatment about 20% of cutaneous skin infection cases progress totoxemia and death.

Treatment typically includes antibiotic therapy. Specific guidelines are available for adults, children, pregnant women, and immunocompromised persons. The differential diagnosis includes multiple entities and thus accurate diagnosis is imperative. Clinical examination coupled with culture and cutaneous biopsy can aid in accurate diagnosis.