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The symptoms of anthrax are determined by the route of transmission of the bacterium, Bacillus anthracis, which causes the infection. There are three forms of anthrax: cutaneous, gastrointestinal, and inhalational [38, 39].

Cutaneous anthrax presents as a small, painless, pruritic papule, which progresses to a vesicle that ruptures and erodes, leaving a necrotic ulcer that later gets covered with a black, painless eschar. Pathognomonic features of anthrax include the presence of an eschar, lack of pain, and edema out of proportion to the size of the lesion. Associated symptoms include swelling of adjacent lymph nodes, fever, malaise, and headache. Cutaneous anthrax is caused by B. anthracis entering a cut or abrasion in exposed areas of the body such as the face, neck, arms, and hands. The case‐fatality rate can be as high as 20% without antibiotic therapy, but 1% with therapy.

Gastrointestinal anthrax presents with symptoms that are more non‐specific. There are two forms: oropharyngeal and intestinal. Oropharyngeal anthrax starts with edematous lesions at the base of the tongue or tonsils that progress to necrotic ulcers with a pseudomembrane. Sore throat, fever, cervical adenopathy, and profound oropharyngeal edema are associated symptoms. The intestinal form of anthrax initially presents with fever, nausea, vomiting, and abdominal pain and tenderness that may progress to hematemesis, bloody diarrhea, and abdominal swelling from hemorrhagic ascites. Gastrointestinal anthrax is caused by consumption of meat contaminated with anthrax. The case‐fatality rate of gastrointestinal anthrax is estimated to be 25‐60%.

Inhalational anthrax initially causes non‐specific symptoms that mimic influenza. These early symptoms are low‐grade fever, non‐productive cough, malaise, and myalgias. Two to three days later, the patient rapidly progresses to severe dyspnea, profuse sweating, high fever, cyanosis, and shock. As many as half of patients develop hemorrhagic meningitis. It is critical that EMS personnel attempt to distinguish any influenza‐like illness from anthrax, because of the narrow window of opportunity for successful treatment. Nasal congestion and rhinorrhea are not common with inhalational anthrax, but more common with influenza‐like illness. Further, shortness of breath is more common in inhalational anthrax and less common with influenza‐like illness. Chest x‐ray demonstrates mediastinal widening or pleural effusion. These findings are the most accurate predictors of inhalational anthrax. Inhalational anthrax can be caused by inhalation of spores, commonly seen following intentional release of aerosolized anthrax, or from the processing of materials from infected animals, such as goat hair. The case‐fatality rate of inhalational anthrax can be as high as 97% without antibiotics and remain as high as 75% despite antibiotic treatment. Human‐to‐human transmission of any form of anthrax is rare.