Influenza viruses spread from person to person primarily through large-particle respiratory droplet transmission. These large-particle droplets require close contact between source and recipient persons, because droplets generally travel relatively short distances through the air. Indirect contact transmission via hand transfer of influenza virus from virus-contaminated surfaces or objects to mucosal surfaces of the face can also occur (CDC, 2021, May 13).
Airborne transmission via small particle aerosols in the vicinity of the infectious individual can 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 (CDC, 2021, May 13).
All respiratory secretions and bodily fluids, including diarrheal stools, of patients with influenza can 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, 2021, May 13).
In Healthcare Settings
Preventing transmission of influenza within a healthcare setting requires a multi-faceted approach. Spread of influenza occurs among patients, healthcare personnel, and visitors. In addition, healthcare personnel can acquire influenza from people in their household or community (CDC, 2021, May 13).
Core infection prevention strategies include:
- Administration of seasonal influenza vaccine
- Implementation of respiratory hygiene and cough etiquette
- 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, 20221, May 13)
Successful implementation of many, if not all, of these strategies is depends on 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, 2021, May 13).
In Long-Term Care Facilities
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, 2020, November 17).
As in any healthcare setting, key prevention strategies in long-term care settings include:
- Annual vaccination
- Infection control
- Antiviral treatment
- Antiviral chemoprophylaxis (CDC, 2020, November 17)
If possible, all residents should receive an influenza vaccine annually before influenza season. Influenza vaccines usually become available to long-term care facilities beginning in September, and influenza vaccination should be offered by the end of October. Informed consent is required to implement a standing order for vaccination, but this does not necessarily mean a signed consent must be present (CDC, 2020, November 17).
Although vaccination by the end of October is recommended, influenza vaccine administered in December or later, even if influenza activity has already begun, is likely to be beneficial. During the majority of influenza seasons, the duration of the season is variable, and influenza activity might not occur in certain communities until February or March (CDC, 2020, November 17).
When a new patient or resident is admitted after the influenza vaccination program has concluded in the facility, the benefits of vaccination should be discussed, educational materials should be provided, and an opportunity for vaccination should be offered to the new resident as soon as possible after admission to the facility (CDC, 2020, November 17).
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 because of shortage. This information is to be reported as part of the CMS Minimum Data Set, which tracks nursing home health parameters (CDC, 2020, November 17).
If one laboratory-confirmed influenza positive case is identified along with other cases of acute respiratory illness in a unit of a long-term care facility, an influenza outbreak might be occurring. Active surveillance should be implemented as soon as possible once one case of laboratory-confirmed influenza is identified. When 2 cases of laboratory-confirmed influenza are identified within 72 hours of each other in residents on the same unit, outbreak control measures should be implemented (CDC, 2020, November 17).
Implementation of outbreak control measures can also be considered as soon as possible when one or more residents have acute respiratory illness with suspected influenza and the results of influenza molecular tests are not available the same day of specimen collection. While unusual, an influenza outbreak can occur outside of the normal influenza season; therefore, testing for influenza viruses and other respiratory pathogens should also be performed during non-influenza season periods (CDC, 2020, November 17).
Influenza prevention recommendations for long-term care facilities include:
- 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 areas) 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, 2020, November 17)
To access the current (2021-2022) CDC influenza recommendations please see:
Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices, United States, 2021–22 Influenza Season