TRANSMISSION
MEANS
Among patients and healthcare personnel (HCP), microorganisms are spread to others through four common routes of transmission: contact (direct and indirect), respiratory droplets, airborne spread and common vehicle.
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CONTACT
Contact is the most important and frequent mode of transmission in the healthcare setting. Organisms are transferred through direct contact between an infected or colonized patient and a susceptible healthcare worker or another person. Patient organisms can be transiently transferred to the intact skin of a healthcare worker (not causing infection) and then transferred to a susceptible patient who develops an infection from that organism—this demonstrates an indirect contact route of transmission from one patient to another. An infected patient touching and contaminating a doorknob, which is subsequently touched by a healthcare worker and carried to another patient, is another example of indirect contact. Microorganisms that can be spread by contact include those associated with antibiotic-resistant organisms (e.g., Methicillin-resistant Staphylococcus aureus (MRSA) and Vancomycin-resistant Enterococci (VRE).
RESPIRATORY DROPLETS
Droplets containing microorganisms can be generated during coughing, sneezing, talking, suctioning and bronchoscopy. They are propelled a short distance before settling quickly onto a surface. They can cause infection by being deposited directly onto nearby environmental surfaces, which can then be touched by a susceptible person who auto inoculates their own surface.
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AIRBORNE SPREAD
When small, particle-size microorganisms remain suspended in the air for long periods of time, they can spread to other people. The CDC has described an approach to reduce transmission of microorganisms through airborne spread in its Guideline for Isolation Precautions in Hospitals. Proper use of personal protective equipment (e.g., gloves, masks and gowns), aseptic technique, hand hygiene and environmental infection control measures are primary methods to protect the patient from transmission of microorganisms from another patient and from the healthcare worker. Personal protective equipment also protects the healthcare worker from exposure to microorganisms in the healthcare setting.
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COMMON VEHICLE
Common vehicle (common source) transmission applies when multiple people are exposed to and become ill from a common inanimate vehicle of contaminated food, water, medications, solutions, devices or equipment. Bacteria can multiply in a common vehicle but viral replication cannot occur. Examples include improperly processed food items that become contaminated with bacteria, waterborne shigellosis and bacteremia resulting from use of intravenous fluids contaminated with Gram-negative organisms.
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