Anthrax infection is a disease that can be acquired following the intentional release of anthrax spores as a biological weapon.

What are the signs and symptoms of anthrax?
Symptoms of disease vary depending on how the disease was contracted, but symptoms usually occur within 7 days.

Cutaneous anthrax is the most common naturally occurring type of infection (>95%) and usually occurs after skin contact with contaminated meat, wool, hides, or leather from infected animals. The incubation period ranges from 1-12 days. The skin infection begins as a small papule, progresses to a vesicle in 1-2 days followed by a necrotic ulcer. The lesion is usually painless, but patients also may have fever, malaise, headache, and regional lymphadenopathy. Most (about 95%) anthrax infections occur when the bacterium enters a cut or abrasion on the skin. Skin infection begins as a raised bump that resembles a spider bite, but (within 1-2 days) it develops into a vesicle and then a painless ulcer, usually 1-3 cm in diameter, with a characteristic black necrotic (dying) area in the center. Lymph glands in the adjacent area may swell. About 20% of untreated cases of cutaneous anthrax will result in death. Deaths are rare if patients are given appropriate antimicrobial therapy.

Inhalational anthrax is the most lethal form of anthrax. Anthrax spores must be aerosolized in order to cause inhalational anthrax. The number of spores that cause human infection is unknown. The incubation period of inhalational anthrax among humans is unclear, but it is reported to range from 1 to 7 days, possibly ranging up to 60 days. It resembles a viral respiratory illness and initial symptoms include sore throat, mild fever, muscle aches and malaise. These symptoms may progress to respiratory failure and shock with meningitis frequently developing.

Gastrointestinal anthrax usually follows the consumption of raw or undercooked contaminated meat and has an incubation period of 1-7 days. It is associated with severe abdominal distress followed by fever and signs of septicemia. The disease can take an oropharyngeal or abdominal form. Involvement of the pharynx is usually characterized by lesions at the base of the tongue, sore throat, dysphagia, fever, and regional lymphadenopathy. Lower bowel inflammation usually causes nausea, loss of appetite, vomiting and fever, followed by abdominal pain, vomiting blood, and bloody diarrhea.

What specific symptoms should I watch for?
People should watch for the following symptoms:

  • Fever (temperature greater than 100 degrees F). The fever may be accompanied by chills or night sweats.
  • Flu-like symptoms
  • Cough, usually a non-productive cough, chest discomfort, shortness of breath, fatigue, muscle aches
  • Sore throat, followed by difficulty swallowing, enlarged lymph nodes, headache, nausea, loss of appetite, abdominal distress, vomiting, or diarrhea
  • A sore, especially on your face, arms or hands, that starts as a raised bump and develops into a painless ulcer with a black area in the center.

Influenza (flu) and inhalation anthrax can have similar symptoms. Does CDC recommend that I get a flu shot to help diagnose anthrax?
You should get a flu shot only to prevent the flu. CDC does not recommend you get the flu shot so doctors can tell whether you have the flu or anthrax. Many illnesses (including anthrax) begin with flu-like symptoms, which include fever, body aches, tiredness, and headaches. In fact, most illnesses with flu-like symptoms are not either the flu or anthrax.

The flu vaccine is the best protection you can get to prevent the flu and its severe complications, especially among those who are at the highest risk (e.g., people older than 65 years old or younger people with chronic disease such as diabetes or heart disease). The flu shot can prevent 70%-90% of flu infections, but it will not prevent illnesses with flu-like symptoms caused by anything other than influenza.

Is there a way to distinguish between early inhalational anthrax and flu?
Early inhalational anthrax symptoms can be similar to those of much more common infections. However, a runny nose is a rare feature of anthrax. This means that a person who has a runny nose along with other common influenza-like symptoms is by far more likely to have the common cold than to have anthrax.

In addition, most people with inhalational anthrax have high white blood cell counts and no increase in the number of lymphocytes. On the other hand, people with infections such as flu usually have low white blood cell counts and an increase in the number of lymphocytes.

Chest X-rays are also critical diagnostic tools. Chest X-rays showed that all patients with inhalational anthrax have some abnormality, although for some patients, the abnormality was subtle. CT scans can confirm these abnormalities.

Is there a quick test that doctors can do to tell whether I have anthrax or an illness like the flu?
Some influenza detection tests give results fairly quickly. However, these tests are not perfect and are not appropriate for every patient. Rapid influenza tests can provide results within 24 hours; viral culture provides results in 3-10 days. However, as many as 30% of samples that test positive for influenza by viral culture may give a negative rapid test result. And, some rapid test results may indicate influenza when a person is not infected with influenza.

Is anthrax contagious?
No. Anthrax is not contagious; the illness cannot be transmitted from person to person.

What are the case fatality rates for the various forms of anthrax?
Early treatment of cutaneous anthrax is usually curative, and early treatment of all forms is important for recovery. Patients with cutaneous anthrax have reported case fatality rates of 20% without antibiotic treatment and less than 1% with it. Although case-fatality estimates for inhalational anthrax are based on incomplete information, the rate is extremely high, approximately 75%, even with all possible supportive care including appropriate antibiotics. Estimates of the impact of the delay in postexposure prophylaxis or treatment on survival are not known. For gastrointestinal anthrax, the case-fatality rate is estimated to be 25%-60% and the effect of early antibiotic treatment on that case-fatality rate is not defined.

Can the presence of Bacillus anthracis spores be detected by a characteristic appearance, odor, or taste?
Bacillus anthracis spores do not have a characteristic appearance (e.g., color), smell, or taste. Spores themselves are too small to be seen by the naked eye, but have been mixed with powder to transport them. The U.S. Postal Service advises that individuals be suspicious of letters or packages with any powdery substance on them, regardless of color. (See

What would be the approximate size of enough Bacillus anthracis spores to cause infection?
They could not be seen by the naked eye but could be seen under a microscope.

How can I know my cold or flu this season is not anthrax?
Many human illnesses begin with what are commonly referred to as “flu-like” symptoms, such as fever and muscle aches. However, in most cases anthrax can be distinguished from the flu because the flu has additional symptoms. In previous reports of anthrax cases, early symptoms usually did not include a runny nose, which is typical of the flu and common cold.

If I have the flu, can I still get anthrax?
Yes, a person could theoretically get both the flu and anthrax, either at the same time or at different times.

How is anthrax diagnosed?
Anthrax is diagnosed by isolating B. anthracis from the blood, skin lesions, or respiratory secretions or by measuring specific antibodies in the blood of persons with suspected cases.

In patients with symptoms compatible with anthrax, providers should confirm the diagnosis by obtaining the appropriate laboratory specimens based on the clinical form of anthrax that is suspected (i.e., cutaneous, inhalational, or gastrointestinal).

Cutaneous – vesicular fluid and blood
Inhalational – blood, cerebrospinal fluid (if meningeal signs are present) or chest X-ray
Gastrointestinal – blood

Preventative Therapy

What is the therapy for preventing inhalational anthrax?
Interim recommendations for postexposure prophylaxis for prevention of inhalational anthrax after intentional exposure to B. anthracis may be found in the MMWR at

What is cipro (ciprofloxacin)?
Ciprofloxacin, or cipro as it is commonly known, is a broad-spectrum, synthetic antimicrobial agent active against several microorganisms. The use of ciprofloxacin is warranted only under the strict supervision of a physician.

Does ciprofloxacin have an expiration date?
Yes. Antibiotics, just like all medicines, have expiration dates. If you received your ciprofloxacin through a pharmacist, the expiration date should be listed on the bottle. If you can’t find it or have questions about the expiration date, contact your pharmacist directly.

What are the side effects of cipro?
Adverse health effects include vomiting, diarrhea, headaches, dizziness, sun sensitivity, and rash. Hypertension, blurred vision, and other central nervous system effects occur in <1% of patients and may be accentuated by caffeine or medications containing theophylline.

What are the guidelines for changing from ciprofloxacin to another antibiotic?
Considerations for choosing an antimicrobial agent include effectiveness, resistance, side effects, and cost. As a measure to preserve the effectiveness of ciprofloxacin against anthrax and other infections, use of doxycycline for preventive therapy may be preferable. As always, the selection of the antimicrobial agent for an individual patient should be based on side-effect profiles, history of reactions, and the clinical setting. For more information about possible adverse reactions from taking antimicrobial prophylaxis see Update: Investigation of Bioterrorism-Related Anthrax and Adverse Events from Antimicrobial Prophylaxis.

Should people buy and store antibiotics?
There is no need to buy or store antibiotics, and indeed, it can be detrimental to both the individual and to the community. First, only people who are exposed to anthrax should take antibiotics, and health authorities must make that determination. Second, individuals may not stockpile or store the correct antibiotics. Third, under emergency plans, the Federal government can ship appropriate antibiotics from its stockpile to wherever they are needed.

Will antibiotics protect me from a bioterrorist event? Should I stockpile them?
CDC does not recommend using antibiotics unless a specific disease has been identified. There are several different agents that could be used for bioterrorism, such as bacteria, viruses, and toxins. Not a single antibiotic (or vaccine) works for all of these agents. Antibiotics only kill bacteria, not viruses or other agents that could also be used in a bioterrorist event. Antibiotics are not harmless drugs. They can cause serious side effects and drug interactions. National and state public health officials have large supplies of needed drugs and vaccines if a bioterrorism event should occur. These supplies can be sent anywhere in the United States within 12 hours.

Who should receive antibiotics for 60 days?
People at risk for inhalational anthrax should receive 60 days of antibiotics. These people include the following:

  1. People who have been exposed to an air space known to have been contaminated with aerosolized B. anthracis.
  2. People who share the air space within a facility where others have acquired inhalational anthrax.
  3. People who have been along the transit pathway of an envelope (or other vehicle) containing B. anthracis that may have been aerosolized.
  4. Unvaccinated laboratory workers who have handled powder that has tested positive for B. anthracis and who may not have used appropriate biosafety precautions.

People who are unsure if they are at risk should discuss any concerns with their healthcare provider or local/state public health department.

When is a 60-day prescription of prophylactic antibiotics not needed?
People who are determined not to be at risk for inhalational anthrax do not need to take the 60-day course of prophylactic antibiotics. Prophylactic antibiotics are not indicated for the prevention of cutaneous anthrax, for hospital personnel caring for patients with anthrax, or for persons who routinely open or handle mail if there has not been a credible threat.

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