Transmission-based Precautions are the Foundation of Infection Prevention

The prevention of the transmission of pathogens goes to the heart of every evidence-based intervention used to control and eliminate hospital-acquired infections (HAIs). Every infection involves three components: a reservoir of microorganisms (i.e., contaminated hands or inanimate surfaces), a susceptible host (i.e., patients, visitors or healthcare workers [HCWs]), and a mechanism of transmission, which refers to the three routes of transmission — airborne, droplet and contact.

The isolation guidelines issued by the Centers for Disease Control and Prevention (CDC) in 1996 created a two-tiered approach: Standard Precautions and Transmission-Based Precautions,1 which draw from protocols established in Universal Precautions (UP) and Body Substance Isolation (BSI) Precautions.

Healthcare Workers as Vectors

Transmission-based precautions are more critical than ever before, especially as the virulence and resistance of superbugs increase and data continue to indicate that HCWs are hosts and carriers of infectious diseases because of colonization or active infection. A new comprehensive review of data from more than 160 studies suggests that hospitals could do a better job of screening healthcare workers for methicillin-resistant Staphylococcus aureus (MRSA) infections.2

Stephan Harbarth of the University Hospitals in Geneva, Switzerland, and Werner Albrich, of the University of the Witwatersand in Johannesburg, South Africa, scrutinized data from approximately169 studies that examined more than 33,000 HCWs from 37 countries. They found that about 6 percent of HCWs were colonized with MRSA, while about 5 percent had active MRSA infections. The authors note, “Poor infection control practices were implicated in both acquisition and transmission of MRSA by personnel, but even good adherence to infection control -— including masks and hand hygiene — did not entirely prevent transmission of MRSA from heavily colonized staff to patients.”

While the time commitment and expense associated with pre-employment and periodical screening of HCWs for MRSA might be challenging for some healthcare facilities, some experts believe that routine surveillance of HCWs during the first stages of an outbreak is prudent, especially in high-risk areas such as surgical intensive care units and burn units.

Harbarth and Albrich note, “HCWs are likely to be important in the transmission of MRSA, most frequently acting as vectors and not as the main sources of MRSA transmission. Thus, good hand hygiene practices remain essential to control the spread of MRSA... Although no single approach to dealing with MRSA in HCWs will work universally, aggressive screening and eradication policies seem justified in outbreak investigations or when MRSA has not reached endemic levels.”

Patients as Vectors

In order for them to work as designed, the most appropriate precautions must be matched to the patient properly.3 In addition to Standard Precautions, one of the three types of precautions relating to the route of transmission should be employed. Airborne Precautions should be used for patients known or suspected to have serious illnesses transmitted by airborne droplet nuclei, including measles, tuberculosis, and varicella.

Droplet Precautions should be implemented for patients known or suspected to have serious illnesses transmitted by large particle droplets, including Haemophilus influenzae Type B disease, including meningitis, pneumonia, epiglottitis, and sepsis, as well as bacterial respiratory infections such as diphtheria, pertussis, pneumonic plague Streptococcal (group A) infections, influenza, mumps, and rubella. Contact Precautions should be used for patients known or suspected to have serious illnesses easily transmitted by direct patient contact or by contact with items in the patient’s environment, such as gastrointestinal, respiratory, skin, or wound infections or colonization with multidrug-resistant organisms of epidemiologic significance such as Clostridium difficile.

Without a confirmed diagnosis, if a patient is suspected of harboring an infection, most experts recommend that Transmission-Based Precautions should be implemented on an empiric basis until a definitive diagnosis is made.3 For example, if a patient presents with a rash with fever, a cough with fever, or a cough and fever with findings on a chest X-ray in an HIV- infected individual, Airborne Precautions should be implemented. If a patient presents with meningitis symptoms, has a severe, persistent cough during a known community outbreak of pertussis, Droplet Precautions should be taken. And finally, Contact Precautions should be used if a patient presents with acute diarrhea in an incontinent patient, diarrhea in an adult on antibiotics, has a history of infections by multidrug-resistant organisms (MDROs). In a guidance document on Transmission-Based Precautions, Johns Hopkins University notes, “The use of Transmission-Based Precautions, including their empiric use in selected circumstances, is designed to reduce the risk of airborne-, droplet- and contact-transmitted infections between hospitalized patients and healthcare staff.”3

Transmission-based Precautions and MRSA

Preventing and controlling MRSA infections requires a comprehensive set of interventions that includes risk assessment, surveillance and active culturing/decolonization, hand hygiene, environmental cleaning, and use of contact precautions, as well as a institutional mindset that incorporates the business case for infection prevention, cultural transformation, and antimicrobial stewardship. The Association for Professionals in Infection Control and Epidemiology (APIC), in its guidance document, “Guide to the Elimination of Methicillin-Resistant Staphylococcus aureus (MRSA) Transmission in Hospital Settings,” notes the importance of contact precautions, the foundation of strategies used in hospitals to prevent the transmission of MRSA and other MDROs.4

The HICPAC guideline, “Management of Multidrug-Resistant Organisms in Healthcare Settings, 2006,” also establishes compliance with Contact Precautions as essential for preventing infections in hospital settings.5 This guideline unequivocably states, “Standard Precautions have an essential role in preventing MDRO transmission, even in facilities that use Contact Precautions for patients with an identified MDRO. Colonization with MDROs is frequently undetected; even surveillance cultures may fail to identify colonized persons due to lack of sensitivity, laboratory deficiencies, or intermittent colonization due to antimicrobial therapy. Therefore, Standard Precautions must be used in order to prevent transmission from potentially colonized patients.”

In addition to strict adherence to Standard Precautions, APIC’s MRSA guideline suggests the following transmission-based steps to take in the fight against MRSA:3

Place known or suspected MRSA patients in a private room or cohort with another patient who has an active MRSA infection but with no other infection

Wear clean, non-sterile gloves when entering the patient’s room, and change gloves after having contact with infectious material. Remove gloves before leaving the patient’s room and perform hand hygiene immediately. After glove removal and handwashing, ensure that hands do not touch potentially contaminated environmental surfaces or items in the patient’s room to avoid transfer of microorganisms to other patients or environments.

Wear a clean, non-sterile gown when entering the room to avoid contamination of clothing by contact with the patient or environmental surfaces. Remove the gown before leaving the patient’s environment, and ensure that clothing does not become contaminated by environmental surfaces to avoid transfer of microorganisms to other patients or environments

Limit the movement and transport of the patient from the room to essential purposes only. If the patient is transported out of the room, take measures to prevent the risk of transmission of MRSA to other patients and environmental surfaces or equipment.

Use dedicated non-critical patient-care equipment while patient is on contact precautions. Adequately clean and disinfect common equipment that is not dedicated to the patient before use with another patient.


1. Garner JS and the Hospital Infection Control Practices Advisory Committee (HICPAC). Guideline for isolation precautions in hospitals, 1996. Infect Control Hosp Epidemiol. 17(1): 53–80 and Am J Infect Control 24(1):24-52.

2. Albrich WC, Harbarth S. Healthcare workers: source, vector, or victim of MRSA? Lancet Infect Dis 2008; 8: 289-301.

3. Johns Hopkins University. Transmission-Based Precautions: Isolation Precaution Guidelines for Hospitals. Accessed at:

4. Association for Professionals in Infection Control and Epidemiology. Guide to the Elimination of Methicillin-Resistant Staphylococcus aureus (MRSA) Transmission in Hospital Settings. 2007.

5. Siegel JD, et al. and the Healthcare Infection Control Practices Advisory Committee (HICPAC). Management of Multidrug-Resistant Organisms in Healthcare Settings, 2006.