Infection Control Considerations

Last updated December 16, 2010. At the current time, this content is considered historical and will not be updated until further notice.

Note: This document is best viewed with Internet Explorer for both format and function.

Modes of Transmission for Influenza Viruses
Infection Control Recommendations

Modes of Transmission for Influenza Viruses

Recommendations on infection control practices are based on available data regarding the modes of transmission of influenza viruses. Influenza viruses potentially can be transmitted through droplet, contact, and airborne modes. Although existing data are limited regarding the contribution of each mode of transmission, a systematic review concluded that influenza virus transmission occurs at close range rather than over long distances (Brankston 2007). Information on the modes of transmission for influenza viruses are outlined below.

Droplet Transmission

Influenza viruses are predominantly transmitted by large droplets (ie, >5 mcm).
Droplets are expelled by coughing and sneezing and generally travel through the air no more than 3 feet from the infected person.
Transmission via large droplets requires close contact between the source and recipient persons, permitting droplets, which do not remain suspended in the air, to come into direct contact with oral, nasal, or ocular mucosa.
Special air handling and ventilation systems are not required to prevent droplet transmission.

Direct and Indirect Contact Transmission

Direct contact transmission involves skin-to-skin contact (such as hand-to-hand) between an infected person and a susceptible person.
The proportion of influenza virus transmission caused by direct or indirect contact remains unknown; however, transmission by these routes can occur.
Influenza viruses can live for 24 to 48 hours on nonporous environmental surfaces and less than 12 hours on porous surfaces (Bean 1982), indicating that transmission can occur when hands that touch contaminated surfaces subsequently come into contact with oral, ocular, or nasal mucosa. Fomite transmission appears to be rare.

Airborne Transmission

Airborne transmission of influenza viruses (ie, transmission via droplet nuclei [<5 mcm], which remain suspended in the air and have the potential to travel farther than several feet) has been suggested in several reports, although evidence to conclusively support airborne transmission of influenza virus is limited (Bridges 2003).
A recent study showed that influenza patients who are coughing often emit aerosol particles that contain influenza virus RNA, and a high proportion of patients produce aerosol particles that are <5 mcm in size (Lindsley 2010). The results support the idea that the airborne route may be a pathway for influenza transmission, especially in the immediate vicinity of an influenza patient. However, further research is needed on the viability of airborne influenza viruses and the risk of transmission.
Available data suggest that airborne transmission does not play a major role in the spread of influenza viruses (Brankston 2007). However, airborne transmission of influenza viruses may occur, at least over short distances (Tellier 2006), and further study is needed to determine the importance of this mode of transmission in healthcare or other settings.
Aerosol-generating procedures (eg, intubation, bronchoscopy, nebulizer treatments) theoretically could promote dissemination of droplet nuclei from infected patients, although this has not been studied for influenza.
There is no evidence to date that droplet nuclei containing influenza viruses can travel through ventilation systems or across long distances, such as can occur with tuberculosis and certain other viral agents.

The CDC has recently updated infection control guidance for the care of patients who have influenza infection (CDC: Prevention strategies for seasonal influenza in healthcare settings). Recommendations from the guidance are summarized below; the full guidance can be accessed at CDC 2010: Prevention strategies for seasonal influenza in healthcare settings.

Infection Control Recommendations

Promote and administer seasonal influenza vaccine for healthcare providers and patients.
Take steps to minimize potential exposures before patients arrive at a healthcare setting, upon entry, and during visits to a healthcare setting.
Monitor and manage ill healthcare personnel.
Adhere to standard precautions.
Adhere to droplet precautions.
Use caution when performing aerosol-generating procedures.

These include some procedures that are usually planned ahead of time, such as bronchoscopy, sputum induction, elective intubation and extubation, and autopsies, as well as some procedures that often occur in unplanned, emergent settings and can be life-saving, such as cardiopulmonary resuscitation, emergent intubation, and open suctioning of airways.
Precautions for aerosol-generating procedures include several actions:

Perform these procedures only on patients with suspected or confirmed influenza if they are medically necessary and cannot be postponed.
Limit the number of healthcare providers present during the procedure to only those essential for patient care and support.
Conduct the procedures in an airborne infection isolation room (AIIR) when feasible.
Consider use of portable HEPA filtration units to further reduce the concentration of contaminants in the air.
Healthcare providers should adhere to standard precautions, including wearing gloves, a gown, and either a face shield that fully covers the front and sides of the face or goggles.
Healthcare providers should wear respiratory protection equivalent to a fitted N-95 filtering facepiece respirator or equivalent N-95 respirator (eg, powered air purifying respirator, elastomeric) during aerosol-generating procedures.
Unprotected healthcare providers should not be allowed in a room where an aerosol-generating procedure has been conducted until sufficient time has elapsed to remove potentially infectious particles.
Conduct environmental surface cleaning following procedures (see section on environmental infection control).

Manage visitor access and movement within the facility.
Monitor influenza activity in the community and the facility.
Implement environmental infection control.

Standard cleaning and disinfection procedures (eg, using cleaners and water to preclean surfaces prior to applying disinfectants to frequently touched surfaces or objects for indicated contact times) are adequate.
Management of laundry, food service utensils, and medical waste should also be performed in accordance with standard procedures.

Implement engineering controls.

Examples of engineering controls include installing physical barriers such as partitions in triage areas or curtains that are drawn between patients in shared areas.
Another important engineering control is ensuring that appropriate air-handling systems are installed and maintained in healthcare facilities.

Train and educate healthcare personnel.

Healthcare administrators should ensure that all healthcare providers receive during orientation job- or task-specific education and training on preventing transmission of infectious agents, including influenza, in the healthcare setting.
Competency should be documented initially and repeatedly, as appropriate, for the specific staff positions.
Key aspects of influenza and its prevention that should be emphasized to all healthcare providers include:

Influenza signs, symptoms, complications, and risk factors for complications
Awareness among healthcare providers that, if they have conditions that place them at higher risk of complications, they should inform their healthcare provider immediately if they become ill with an influenza-like illness so they can receive early treatment if indicated
Central role of administrative controls such as vaccination, respiratory hygiene and cough etiquette, sick policies, and precautions during aerosol-generating procedures
Appropriate use of personal protective equipment, including respirator fit testing and fit checks
Use of engineering controls and work practices, including infection control procedures to reduce exposure

Administer antiviral treatment and chemoprophylaxis of patients and healthcare personnel when appropriate.
Underscore considerations for healthcare personnel at higher risk for complications of influenza:

Healthcare providers at risk for complications from influenza include pregnant women and women up to 2 weeks postpartum, persons 65 years old and older, and persons with chronic diseases such as asthma, heart disease, diabetes, diseases that suppress the immune system, certain other chronic medical conditions, and morbid obesity.
Provide vaccination and early treatment with antiviral medications.
Healthcare providers at higher risk for complications should check with their healthcare provider if they become ill so that they can receive early treatment.


Home	Mission & Activities	About Us	Your Support	Contact Us