Isolation & Quarantine Measures in Response to a Smallpox Emergency

Additional Transmission-Based Precautions

Additional Transmission-Based Precautions are designed for patients documented or suspected to be infected with highly transmissible or epidemiologically important pathogens for which additional precautions beyond Standard Precautions are needed to prevent or interrupt transmission in hospitals. Three types of transmission-based precautions with examples of the biological agents that are transmitted by this route and require these types of precautions. All three types of Transmission-Based Precautions should be followed for smallpox.

Airborne Precautions

Airborne Precautions (TB, varicella, measles, etc.) are designed to reduce the risk of airborne transmission of infectious agents and apply to patients known or suspected to be infected with epidemiologically important pathogens that can be transmitted by this route.

Airborne transmission occurs by dissemination of either airborne droplet nuclei (small-particle residue [5 microns or smaller in size] of evaporated droplets that can remain suspended in the air for longer periods of time) or dust particles containing the infectious agent. Microorganisms carried in this manner can be dispersed more widely by air currents and may become inhaled by or deposited on a susceptible host within the same room or over a longer distance from the source patient, depending on environmental factors. Special air handling and ventilation are required to prevent airborne transmission. Airborne precautions (masks, special air handling room requirements) provides respiratory protection for workers who must share airspace with the infectious patient and prevents potentially contaminated air from the patient’s room from getting to other areas of the hospital.

Droplet Precautions

Droplet Precautions are designed to reduce risk of droplet transmission of infectious agents. Droplet transmission involves contact of the conjunctivae or the mucous membranes of the nose or mouth of a susceptible person with large-particle droplets (larger than 5 microns in size) containing microorganisms generated from a person who has a clinical disease or who is a carrier of the microorganism.

Droplets are generated from the source person primarily during coughing, sneezing, or talking and during the performance of certain procedures such as suctioning and bronchoscopy. Transmission via large-particle droplets requires close contact between source and recipient persons, because droplets do not remain suspended in air and generally travel only short distances, (usually 3 ft or less). Because droplets do not remain suspended in air, special air handling and ventilation are not required to prevent transmission.

Contact Precautions

Contact Precautions are designed to reduce the risk of transmission of epidemiologically important microorganisms by direct or indirect contact. Direct-contact transmission involves skin-to-skin contact and physical transfer of microorganisms to a susceptible host from and infected or colonized person, such as occurs when personnel turn patients, bathe patients, or perform other patient-care activities that require physical contact. Direct-contact transmission also can occur between two patients (e.g., by hand contact), with one serving as the source of infectious microorganisms and the other as a susceptible host.

Indirect-contact transmission involves contact of a susceptible host with a contaminated object in the patient’s environment.

Contact Precautions apply to specified patients known or suspected to be infected or colonized (presence of microorganism in or on patient but without clinical signs and symptoms of infection) with epidemiologically important microorganisms that can be transmitted by direct or indirect contact. Contact precautions (disposable protective clothing in addition to gloves, handwashing, and splash precautions) help prevent direct contact but also prevent the health-care provider from carrying infectious materials to areas outside of the room. 

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