



Bacillus anthracis bacteria (Courtesy of the CDC Public Health Image Library)


What is anthrax?

Anthrax is an acute infectious disease caused by the spore-forming bacterium Bacillus anthracis. Anthrax most commonly occurs in wild and domestic lower vertebrates (cattle, sheep, goats, camels, antelopes, and other herbivores), but it can also occur in humans when they are exposed to infected animals or to tissue from infected animals or when anthrax spores are used as a bioterrorist weapon. The Centers for Disease Control and Prevention classifies agents with recognized bioterrorism potential into three priority areas (A, B and C). Anthrax is classified as a Category A agent. Category A agents are those that:

  • Pose the greatest possible threat for a bad effect on public health
  • May spread across a large area or need public awareness
  • Need a great deal of planning to protect the public’s health


How common is anthrax?

Prior to September 11, 2001, anthrax primarily occurred in workers that process animal hides, hair, bone, and wool. Anthrax is now a bioterrorist agent that has targeted  postal workers, television personnel, and government officials in the form of powder in mail envelopes. Wyoming has not had a case since 1956. 


What are the symptoms for anthrax?

  • Flu-like symptoms.

Cutaneous anthrax lesion on the neck

 (Courtesy of the CDC Public Health Image Library)   


How soon after exposure do symptoms appear?

Most symptoms begin 1-7 days after exposure. This period may be as long as 60 days.


How is anthrax spread?

Anthrax is generally transmitted by the following methods:

  • Skin (cutaneous) – Most anthrax infections occur when people touch contaminated animal products like wool, bone, hair, and hide. However, through bioterrorist efforts the infectious agent can also be spread by direct contact with the powdered form of the bacteria. The infection occurs when the bacteria enters a cut or scratch on the skin.
  • Inhalation – Some anthrax infections occur when people breathe in the spores of the bacteria. (The spore is the inactive form of the bacterium that becomes activated once in contact with a warm, moist environment like the human lung.)
  • Gastrointestinal – Some people may contract anthrax through infected meat.


How is anthrax diagnosed?

A diagnosis of Anthrax is based on a combination of clinical signs and symptoms and specialized confirmatory laboratory tests depending on the type of infection (cutaneous, inhalation, etc.) Tests can include chest x-ray (inhalation), Gram stain and culture should be performed on specimens of blood, CSF, pleural fluid, tissue biopsy, and cutaneous lesions.  Your healthcare provider will determine if laboratory testing is needed. 


What is the treatment for anthrax?

Antibiotics (generally ciprofloxacin or doxycycline possibly with additional antibiotics) for 60 days in inhalational or systemic disease, or in cutaneous disease with the risk of inhalational exposure; in isolated cutaneous disease without risk of inhalational exposure 7-10 days of antibiotic treatment is usually sufficient.


Is there any treatment for an individual that was exposed to anthrax but has not had symptoms?

Individuals potentially exposed through direct contact to the spores or items contaminated with the spores, or through air that may contain spores, are given antibiotics to prevent an infection.


What should people do when they get a letter or package with unexplained, suspicious powder?

  • Do not shake or empty the contents of any suspicious package or envelope.
  • Put the package or envelope down on a stable surface; do not sniff, touch, taste, or look closely at it or at any contents which may have spilled.
  • Alert others in the area about the suspicious package or envelope. Leave the area, close any doors, and take actions to prevent others from entering the area. If possible, shut off the ventilation system. Avoid having your clothes or contaminated skin come into contact with other people, objects, or surfaces. Minimize contact between exposed persons and non-exposed persons.
  • Wash hands with soap and water to prevent spreading potentially infectious material to face or skin. Be careful not to spread potential contamination to other people, objects, or surfaces. If possible take action to prevent non-exposed persons from using the washroom after the exposed person(s).  
  • If at work, notify a supervisor, a security officer, or a law enforcement official. If at home, contact the local law enforcement agency. Emergency responders should notify public health officials.
  • If possible, create a list of persons who were in the room or area when this suspicious letter or package was recognized and a list of persons who also may have handled this package or letter. Give this list to responders on the scene.


Is the anthrax vaccine available to the public?

A vaccine has been developed for anthrax that is protective against invasive disease, but it is currently only recommended for high-risk populations (see below). CDC and academic partners are continuing to support the development of the next generation of anthrax vaccines.


Who should be vaccinated against anthrax?


  • Persons who work directly with the organism in the laboratory.
  • As part of post-exposure prophylaxis for persons exposed to an intentional release of anthrax. 


For additional information, visit the Centers for Disease Control.