Anthrax

Symptoms

The average incubation period for anthrax is up to 7 days, but it can take 60 days or longer for symptoms to develop.² Symptoms depend on how the infection was acquired.

Cutaneous anthrax

Cutaneous anthrax usually occurs when spores from the bacteria enter a cut or scrape on the skin. Cutaneous anthrax infection has the following characteristics:

• Skin infection begins as a small, raised bump that might itch—similar to an insect or spider bite.
• Within 1 to 2 days, the bump develops into a fluid-filled blister about 1 cm (0.4 in.) to 3 cm (1.2 in.) in diameter. Within 7 to 10 days, the blister usually has a black center of dying tissue (eschar) surrounded by redness and swelling. The blister is usually painless.
• Additional blisters may develop.

Other symptoms may include:

• Swollen lymph nodes close to the area of the blister.
• Fever.
• Headache.
• A general feeling of discomfort.

Gastrointestinal anthrax

No confirmed cases of gastrointestinal anthrax have been reported in the United States.² This form of anthrax occurs after eating meat contaminated with the bacteria that cause anthrax. Gastrointestinal anthrax can be more serious than cutaneous anthrax but can be treated effectively with prompt use of antibiotics. But if untreated, gastrointestinal anthrax causes:

• Ulcers at the base of the tongue or tonsils.
• Sore throat.
• Loss of appetite.
• Vomiting.
• Fever.

These symptoms are followed by:

• Abdominal pain.
• Vomiting of blood.
• Bloody diarrhea.

Within 2 to 4 days after these symptoms develop, fluid (ascites) fills the abdomen; shock and death usually follow within 2 to 5 days.

Inhalational anthrax

The most lethal form of exposure occurs from inhalational anthrax . The incubation period for this form of anthrax may be 60 days or more, although it is usually 2 to 3 days. Initial symptoms can include:

• Sore throat.
• Mild fever.
• Muscle aches.

Symptoms can progress rapidly after just a few days to include:

• Severe difficulty with breathing.
• Shock, which can develop rapidly.
• Meningitis, which develops frequently.

Death can occur within 24 to 36 hours after such complications occur. Respiratory symptoms may be similar to those of pneumonia.

After the disease becomes severe, it is difficult to treat, and survival is unlikely. Inhalational anthrax is not contagious. You must inhale the spores from the environment to develop this form of anthrax. Even with the outbreaks in 2001, this type of exposure is still very rare.

The symptoms of inhalational anthrax infection may resemble those of influenza (flu), except for these key differences:³

• Shortness of breath, which may occur with anthrax infection, is not a common symptom of the flu.
• A runny nose, which often occurs with the flu, is not common in anthrax.

Oropharyngeal anthrax

This is the least common form of anthrax. The incubation period is from 1 to 7 days. Initial symptoms include:

• Fever.
• Swollen lymph nodes in the neck.
• Severe throat pain.
• Difficulty swallowing.
• Ulcers at the base of the tongue.

As infection progresses, swelling can make breathing difficult.

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Author:	Maria G. Essig, MS, ELS	Last Updated: June 20, 2008
Medical Review:	Kathleen Romito, MD - Family Medicine Christine Hahn, MD - Epidemiology
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