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Fact Sheets

Biological and Chemical Agents of Concern

Download fact sheets covering the basics on transmission, diagnosis, treatment, and decontamination of agents that have been used for terrorism or are considered a serious threat.

Bacillus anthracis (Anthrax)

Anthrax is a very serious bioterrorism threat. B. anthracis was developed by several countries as part of their biological weapons (BW) programs, and autonomous groups have also demonstrated the intent to use the bacterium in acts of terrorism.

View the Bacillus anthracis (Anthrax) Fact Sheet

Botulinum Toxin (Botulism)

Botulinum toxins pose a major threat as biological weapons because they are extremely potent and lethal; some of the toxins are relatively easy to produce and transport; and people with botulism require prolonged intensive hospital care.

View the Botulinum Toxin (Botulism) Fact Sheet

Burkholderia Mallei and Pseudomallei (Glanders and Melioidosis)

Glanders is caused by infection with the bacterium Burkholderia mallei, and melioidosis is caused by Burkholderia pseudomallei. Both have the potential to produce fatal disease and have been identified by the CDC as Category B biological agents. HHS has identified these diseases as top priorities for development of medical countermeasures.

View the Burkholderia Mallei and Pseudomallei (Glanders and Melioidosis) Fact Sheet

Coronaviruses: SARS, MERS, and COVID-19

Coronaviruses (CoV) are a family of RNA viruses that typically cause mild respiratory disease in humans. However, the 2003 emergence of the severe acute respiratory disease coronavirus (SARS-CoV) demonstrated that CoVs are also capable of causing outbreaks of severe infections in humans. A second severe CoV, Middle East respiratory syndrome coronavirus (MERS-CoV), emerged in 2012 in Saudi Arabia. More recently, a novel coronavirus was identified in Wuhan, China, in December 2019.

View the Coronaviruses: SARS, MERS, and COVID-19 Fact Sheet


Cyanide is a naturally occurring chemical, found in many plants, that has been used in conventional warfare and poisoning for 2 millennia. It is highly lethal, whether inhaled as a gas, ingested in solid form, or absorbed through topical exposure. Two notorious incidents in recent history—the Jonestown Massacre in 1978 and the Tylenol poisonings in 1982—highlight the lethality of this poison.

View the Cyanide Fact Sheet

Francisella Tularensis (Tularemia)

F. tularensis is considered to be a serious potential bioterrorist threat because it is one of the most infectious pathogenic bacteria known—inhalation of as few as 10 organisms can cause disease—and it has substantial capacity to cause serious illness and death. The bacterium was developed into an aerosol biological weapon by several countries in the past.

View the Francisella Tularensis (Tularemia) Fact Sheet

Hemorrhagic Fever Viruses (HFVs)

Some HFVs are considered to be a significant threat for use as biological weapons due to their potential for causing widespread illness and death.  Ebola, Marburg, Junin, Rift Valley fever, and yellow fever viruses have been deemed to pose a particularly serious threat, and in 1999 the HFVs were classified as category A bioweapons agents by the U.S. Centers for Disease Control and Prevention (CDC).

View the Hemorrhagic Fever Viruses (HFVs) Fact Sheet

Influenza A (H5N1)

Wild birds are the natural reservoir for influenza A viruses. These viruses are well adapted to the bird hosts and therefore are called avian influenza (AI) viruses, in contrast to human-adapted influenza A viruses that cause seasonal flu. AI viruses can be of many genotypes based on their surface antigens and are frequently found in both wild birds and domestic poultry. 

View the Novel Highly Pathogenic Influenza A (H5N1) Medical Countermeasures Fact Sheet


Monkeypox is a rare viral infection that is thought to typically spread from close person-to-person contact through large respiratory droplets, direct contact with skin lesions or bodily fluids, or indirect contact via contaminated clothing or linens. Symptoms include fever and chills, headache, muscle aches, swollen lymph nodes, and a rash similar to chickenpox that can spread throughout the body and notably on the palms of the hands.

View the Monkeypox Fact Sheet

Nerve Agents

Nerve agents are a class of chemicals grouped together based on their common mechanism of action, which is interruption of vital nerve transmissions to various organs.

View the Nerve Agents Fact Sheet

Pulmonary or Choking Agents

Pulmonary agents (also known as “choking” agents) compose a class of chemical compounds that disrupt normal breathing.

View the Pulmonary or Choking Agents Fact Sheet

Ricin Toxin

The CDC has classified ricin toxin as a Category B threat agent. Category B agents are the second highest priority agents because they can be disseminated with moderate ease, they cause moderate morbidity and low mortality, and they “require specific enhancements of CDC’s diagnostic capacity and enhanced disease surveillance.”

View the Ricin Toxin Fact Sheet

Rickettsia prowazekii (Epidemic Typhus)

Although never employed as a bioweapon to date, R. prowazekii was studied as a candidate for airborne dissemination by Japan during World War II and by the former Soviet Union during the 1970s because of its potential lethality and its ability to spread between humans via lice. Typhus has the potential to produce fatal disease and has been identified by the CDC as a Category B biological agent.

View the Rickettsia prowazekii (Epidemic Typhus) Fact Sheet

Sulfur Mustard (Blister Agent)

Blister agents, also known as vesicants, are a class of chemical weapon first used in combat during World War I. The prototypical and most common blister agent is sulfur mustard (SM) (bis-(2-chloroethyl) sulfide), known as mustard gas.

View the Sulfur Mustard (Blister Agent) Fact Sheet

Variola Virus (Smallpox)

Smallpox was used as a biological weapon during the French and Indian Wars, (1754 to 1767) , and in the 1980s, was developed into an aerosol biological weapon by the Soviet Union.

View the Variola Virus (Smallpox) Fact Sheet

Yersinia Pestis (Plague)

Y. pestis was developed as an aerosol weapon that, when deployed, can cause primary pneumonic plague, a highly lethal, and contagious form of plague.

View the Yersinia Pestis (Plague) Fact Sheet