Transmission and Spread of Anthrax

How is anthrax transmitted?

Infection occurs when the spores enter the body through a cut, abrasion, or open sore, referred to as cutaneous anthrax, or by ingestion or inhalation of the spores. Once inside the body, anthrax spores germinate into bacteria that then multiply and secrete three proteins: protective antigen (PA), lethal factor (LF), and edema factor (EF). Individually these proteins are non-toxic, but they can become lethal if allowed to combine and interact on and within the cells of the exposed human or animal.

Is anthrax disease contagious?

No. Inhalational anthrax disease is not considered a communicable disease that is spread from person-to-person like the flu or common cold. Even if you have symptoms of anthrax disease, you are not contagious to anyone with whom you come in contact.

Can anthrax spores be spread?

While the disease itself is not a communicable disease, it is possible for anthrax spores to be re-aerosolized or spread long distances through the air. An analysis of the anthrax attack on the Hart Senate Office Building revealed that people outside the building were exposed to the anthrax spores released inside the building 5,6. This finding supports both the idea that the anthrax spores used could travel long distances through the air and the idea of cross-contamination, whereby individuals outside the building may have been exposed through contact with re-aerosolized spores from individuals who had been inside the building.

How can I help protect myself against anthrax?

The best way to protect against infectious diseases is to get vaccinated before exposure. A vaccine is currently available for pre-exposure protection against anthrax. It is called BioThrax® (Anthrax Vaccine Adsorbed).

The safety and efficacy of BioThrax have not been established in pediatric or geriatric populations.

BioThrax may not protect all individuals vaccinated, particularly patients with impaired immune responses due to congenital or acquired immunodeficiency or immunosuppressive therapy. Individuals are not considered protected until they have completed the three-dose primary vaccination series.

Next: Why Be Concerned About Anthrax

5 Sternberg S. Study: People outside Senate office infected with anthrax. USA Today. Jan 8, 2007.

6 Doolan et al. The US Capitol Bioterrorism Anthrax Exposures: Clinical Epidemiological and Immunological Characteristics. Journal of Infectious Diseases. 2007. 195: 174-84.




BioThrax is a vaccine indicated for the active immunization for the prevention of disease caused by Bacillus anthracis in persons 18 through 65 years of age. BioThrax is approved for:

  1. Pre-exposure prophylaxis of disease in persons at high risk of exposure.
  2. Post-exposure prophylaxis of disease following suspected or confirmed Bacillus anthracis exposure, when administered in conjunction with recommended antibacterial drugs.

The efficacy of BioThrax for post-exposure prophylaxis is based solely on studies in animal models of inhalational anthrax.


Severe allergic reaction (e.g. anaphylaxis) after a previous dose of BioThrax or a component of the vaccine.

Adverse Reactions

The most common (≥10%) local (injection-site) adverse reactions observed in clinical studies were tenderness, pain, erythema, edema, and arm motion limitation. The most common (≥5%) systemic adverse reactions were muscle aches, headache, and fatigue. Acute allergic reactions, including anaphylaxis, have occurred with BioThrax.

Warnings and Precautions

Vaccination with BioThrax should be avoided by individuals with a history of anaphylactic or anaphylactic-like reaction following a previous dose of BioThrax or any component of the vaccine. If BioThrax is used during pregnancy, or if the patient becomes pregnant during the immunization series, the patient should be apprised of the potential hazard to the fetus. Pregnant women should not be vaccinated unless the potential benefits of vaccination have been determined to outweigh the potential risk to the fetus. It is not known whether BioThrax is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when BioThrax is administered to a nursing woman.

BioThrax should be administered with caution to persons with a possible history of latex sensitivity since the vial stopper contains dry natural rubber.