Terms and Definitions

Aerosol, aerosolized: A suspension of liquid droplets or small (< 5µm) particles in the air. Aerosolized biological agents may remain suspended in air for long periods and may travel long distances. Aerosol transmission occurs when particles containing a biological agent are inhaled by another person. Aerosols are typically generated by coughing. However, aerosols can be weaponized in the case of an intentional attack with a biological weapon.

Airborne precautions: Airborne precautions prevent transmission of infectious agents that remain infectious over long distances when suspended in the air.

Antibiotic susceptibility: Vulnerability of a specific bacterial strain to antibiotic treatment. Some strains are resistant to specific antibiotics, so antibiotic susceptibility must be determined before drugs are chosen for prophylaxis or treatment.

Avirulent: A biological agent is avirulent when it does not cause disease in a host.

Biovar: formerly called a biotype, a biovar is group of bacterial strains distinguishable from other strains of the same species on the basis of physiological characters.

Epidemic: A sudden severe outbreak of disease within a population, producing more than the expected number of cases of disease during a given time period.

Endemic: A disease that is constantly present to a greater or lesser degree in a human or animal population in a specific geographic location.

Incubation period: The time from exposure to a biological agent to the appearance of symptoms in infected persons.

Infectious dose: The amount of pathogen (measured in number of organisms) required to cause infection in the host.

Isolated, isolation and quarantine: Public health measures implemented to stop the spread of communicable disease. Isolation refers to the separation and restriction of movement of people who are sick with an infectious illness from those who are not infected. Quarantine refers to the separation and restriction of movement of persons who are not currently sick but have been exposed to an infectious agent and may become sick and/or spread illness to others. In most cases, isolation and quarantine are voluntary. However, federal, state, and local governments do have the authority to enforce the isolation and quarantine of sick and infected people.

Negative pressure isolation room: A patient isolation room, generally used with TB patients, that is designed to direct air flow from outside corridors and rooms into the isolation room, preventing the chance for contaminated air to flow to other parts of a building.

Of Concern: Specific characteristics of biological agents, including high infectious properties, easy person-to-person transmission, lack of countermeasures, and easy weaponization or aerosolization, which qualify them as a high priority threat.

Pandemic: A widespread epidemic that affects populations in many different countries and possibly around the world.

Post-exposure prophylaxis: A short-term treatment to reduce the likelihood of infection after potential exposure to a pathogen. For bioterrorist agents (bacteria, viruses, or toxins), post-exposure prophylaxis usually occurs in the form of a vaccine, if one is available.

Respiratory droplet transmission: Droplet transmission occurs when relatively large (>5 microns) particles containing a biological agent are propelled from an infected person over relatively short distances (3-6 feet) and deposited onto mucous membranes (usually mouth or nose) of another person or an environmental surface.

Respiratory droplet precautions: Use of gown, gloves, eye protection, and surgical masks to protect against respiratory droplet particles.

Standard precautions: Precautions (such as use of personal protective equipment) to prevent skin and mucous membrane exposure when contact with any blood or other body fluids is anticipated. Standard precaution guidelines are based on the principle that all blood, body fluids, secretions, nonintact skin, mucous membranes, and excretions except sweat may contain transmissible infectious agents.

Supportive therapy: An intervention to relieve symptoms of infection in patients. Supportive care can include intravenous fluids or medicine for pain or fever relief.

Surveillance and containment: This refers to detection of cases through various reporting mechanisms and, in the case of smallpox and other communicable diseases, isolation of infected patients and vaccination of potentially exposed persons and their close contacts.

Virion: A complete virus particle, including genetic material and protein coat, as it would exist outside of a cell.

Virulent: A biological agent is virulent when it has the ability to overcome the host’s immune defenses and cause disease. Virulence is a measure of the severity of disease that an agent is capable of causing.

Weaponized: In the context of biological weapons, ‘weaponization’ refers to the act of adapting a biological agent for use as a weapon. When a biological agent is referred to as having been weaponized, it usually means that it has been manipulated or treated in such a way as to improve its effectiveness as a weapon such as making it more virulent, more easily disseminated as an aerosol, or more stable.

Zoonosis, zoonotic disease: a disease that can be spread from wild or domesticated animals to humans. Examples of zoonotic diseases include anthrax, plague, and tularemia. Much of the world’s emerging infectious diseases are zoonotic.