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Traditionally, influenza viruses have been thought to spread from person to person primarily through large-particle respiratory droplet transmission (eg, when an infected person coughs or sneezes near a susceptible person). Transmission via large-particle droplets requires close contact between source and recipient persons, because droplets generally travel only short distances (approximately 6 feet or less) through the air. Indirect contact transmission via hand transfer of influenza virus from virus-contaminated surfaces or objects to mucosal surfaces of the face (eg, nose, mouth) may also occur (CDC, 2018e).
Airborne transmission via small particle aerosols in the vicinity of the infectious individual may also occur; however, the relative contribution of the different modes of influenza transmission is unclear. Airborne transmission over longer distances, such as from one patient room to another, has not been documented and is thought not to occur. All respiratory secretions and bodily fluids, including diarrheal stools, of patients with influenza are considered to be potentially infectious; however, the risk may vary by strain. Detection of influenza virus in blood or stool in influenza infected patients is very uncommon (CDC, 2018e).
In Healthcare Settings
Healthcare settings include, but are not limited to, acute-care hospitals; long-term care facilities, such as nursing homes and skilled nursing facilities; physicians’ offices; urgent-care centers, outpatient clinics; and home healthcare (CDC, 2018e).
Preventing transmission of influenza within a healthcare setting requires a multi-faceted approach. Spread of influenza virus can occur among patients, healthcare personnel, and visitors; in addition, healthcare personnel may acquire influenza from people in their household or community(CDC, 2018e).
Core infection prevention strategies include:
- Promote and administer seasonal influenza vaccine
- Implement respiratory hygiene and cough etiquette
- Appropriate management of ill healthcare personnel
- Adherence to infection control precautions for all patient-care activities and aerosol-generating procedures
- Implementation of environmental and engineering infection control measures (CDC, 2018e).
Successful implementation of many, if not all, of these strategies is dependent on the presence of clear administrative policies and organizational leadership that promote and facilitate adherence to these recommendations among the various people within the healthcare setting, including patients, visitors, and healthcare personnel (CDC, 2018e).
In Long-Term Care Facilities
Long-term care facilities are institutions, such as nursing homes and skilled nursing facilities, which provide healthcare to people (including children) who are unable to manage independently in the community. This care may represent custodial or chronic care management or short-term rehabilitative services (CDC, 2019i).
Influenza can be introduced into a long-term care facility by newly admitted residents, healthcare workers, or visitors. Spread of influenza can occur between and among residents, healthcare providers, and visitors. Residents of long-term care facilities can experience severe and fatal illness during influenza outbreaks (CDC, 2019i).
As in any healthcare setting, key prevention strategies in long-term care settings include:
- Annual vaccination
- Infection control
- Antiviral treatment
- Antiviral chemoprophylaxis (CDC, 2019i)
If possible, all residents should receive trivalent inactivated influenza vaccine (TIV) annually before influenza season. In the majority of seasons, TIV will become available to long-term care facilities beginning in September, and influenza vaccination should begin as soon as vaccine is available. Informed consent is required to implement a standing order for vaccination, but this does not necessarily mean a signed consent must be present (CDC, 2019i).
Since October 2005 the Centers for Medicare and Medicaid Services (CMS) has required nursing homes participating in Medicare and Medicaid programs to offer all residents influenza and pneumococcal vaccines and to document the results. Each resident is to be vaccinated unless contraindicated medically, the resident or legal representative refuses vaccination, or the vaccine is not available (CDC, 2019).
Even if it is not influenza season, influenza testing should occur when any resident of a long-term care facility has signs and symptoms that could be due to influenza, and especially when two residents or more develop respiratory illness within 72 hours of each other. Because of the high risk of morbidity and mortality in older adults, daily active surveillance is recommended for respiratory illness among ill residents, healthcare personnel, and visitors to the facility (CDC, 2019i).
If influenza is already present in a long-term care facility, residents who are symptomatic should stay in their own rooms as much as possible. They should be restricted from participation in common activities and should have meals served in their rooms. If an outbreak is widespread, large-group activities should be limited and all meals should be offered in resident rooms. New admissions or transfers to wards with symptomatic residents should be avoided (CDC, 2019i).
A posted notice should alert visitors to the presence of influenza in a facility. The spread of influenza can be reduced by restricting visitation and excluding ill people from visiting the facility during an outbreak. During community outbreaks of influenza, children should also be restricted from visiting residents (CDC, 2019i).
Healthcare personnel with respiratory symptoms should be monitored and those with influenza-like symptoms should stay home until at least 24 hours after they no longer have a fever (CDC, 2019i).
Influenza Prevention Recommendations for Long-Term Care Facilities
- Residents with signs and symptoms of influenza-like illness should be tested for influenza.
- Residents being tested for other respiratory pathogens during non-influenza season periods should also be tested for influenza.
- Facilities should implement daily active surveillance for respiratory illness among ill residents, healthcare personnel, and visitors to the facility.
- Standard and Droplet Precautions should be used for all residents with suspected or confirmed influenza.
- Influenza antiviral treatment and chemoprophylaxis should be administered to residents and healthcare personnel according to current recommendations. Treatment should not wait for laboratory confirmation of influenza.
- Residents in the entire long-term care facility (not just currently impacted wards) should receive antiviral chemoprophylaxis as soon as an influenza outbreak is determined.
- Antiviral chemoprophylaxis can be considered or offered to unvaccinated personnel who provide care to people at high risk of complications.
- Drug-resistant viruses are a possibility and should be considered. (CDC, 2017)
Healthcare personnel who get vaccinated help to reduce the following:
- Transmission of influenza (to patients as well as their own family)
- Staff illness and absenteeism
- Influenza-related illness and death, especially among people at increased risk for severe influenza illness
Influenza outbreaks in hospitals and long-term care facilities have been attributed to low influenza vaccination coverage among healthcare personnel. Higher vaccination levels among healthcare personnel have been associated with a lower risk of healthcare facility-associated influenza cases (CDC, 2019i).
Current ACIP Influenza Recommendations
To access the current (2020–2021) ACIP influenza recommendations please see:
Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices, United States, 2020–2021 Influenza Season