Clusters of influenza-like illness (ILI) or acute respiratory illness (ARI) identified in healthcare settings – among patients, residents, visitors, or healthcare personnel – may represent outbreaks and should be reported to public health. 24/7 public health agency contact information is available here. The symptoms and syndromes associated with ILI and ARI can be similar for different respiratory viruses (e.g., respiratory syncytial virus (RSV), influenza, SARS-CoV-2, rhinovirus). This page includes resources to assist healthcare facilities and public health agencies when responding to ILI or ARI while diagnostic testing, to determine the specific virus causing illness, is pending or unavailable. For situations in which the causative agent has already been established, refer to pathogen-specific materials, such as: influenza virus, SARS-CoV-2, respiratory syncytial virus (RSV), rhinovirus, human metapneumovirus, and human parainfluenza virus.
ILI is a non-specific syndrome defined as fever (temperature of 100° F or greater) and cough and/or sore throat. It is used for influenza surveillance worldwide. ILI can be caused by influenza virus infection and infections with other respiratory viruses.
ARI is a non-specific syndrome that can be caused by infection with different respiratory pathogens. ARI typically involves the airways within the nose and throat (i.e., the upper respiratory tract) and may or may not include fever (measured by a thermometer) or feverishness (i.e., self-reported sense of fever). ARI is generally defined as the presence of two or more signs or symptoms such as fever, cough, runny nose or nasal congestion, or sore throat).
Fever can be difficult to identify in older adults; for residents in long-term care facilities, IDSA Guidelines define fever for this population as follows:
A single oral temperature >100°F (>37.8°C); or
Repeated oral temperatures >99°F (>37.2°C) or rectal temperatures >99.5°F (>37.5°C); or
An increase in temperature of >2°F (>1.1°C) over the baseline temperature
Considerations for investigation and reporting of ILI or ARI in healthcare settings:
Considerations for All Healthcare Settings
Additional Investigation by Facility
In general, healthcare facilities should investigate situations in which there is an elevated risk for exposure and disease transmission within their facility.
This may include situations in which patients with ILI or ARI receive care without appropriate Transmission-Based Precautions (TBP) or develop ILI or ARI several days into an admission (i.e., after the incubation period for likely causative agents).
Facilities should be mindful of illness among healthcare personnel (HCP) or visitors as potential points of introduction, and for HCP-to-HCP transmission associated with shared break areas or carpooling.
Reporting to Public Health
In general, healthcare facilities should report any suspected clusters or outbreaks to the appropriate public health agency (i.e., situations involving healthcare transmission). 24/7 public health agency contact information is available here.
Facilities should promptly report situations involving unexpected and concerning disease features (e.g., unusually severe illness, significant rates of illness among staff).
Facilities should report situations involving a cluster of patients/residents with ILI or ARI where exposure(s) likely occurred within the healthcare facility (i.e., epi-linked cases).
Epi-linkage may be defined based on overlap in location (e.g., unit or ward), or the potential for having shared HCP, within a disease appropriate time-period. For ILI or ARI, seven days may be reasonable relative to common viral respiratory pathogens (e.g., SARS-CoV-2 and influenza).
Public health may be able to support access to expanded diagnostic testing if there are challenges in determining a causative agent.
Facilities should be aware of reporting requirements in their jurisdiction and contact public health with any questions.
Outbreak Definition
Specific outbreak definitions are not included in this table.
Pathogen-specific recommendations should be used once diagnostic clarity is achieved.
Declaration of an outbreak in a healthcare facility, in the absence of a known etiologic agent, is uncommon and should follow consultation with public health.
Public health may assist with outbreak definition development when needed.
CDC recommends initiation of Transmission Based Precautions (TBP) in healthcare settings when patients or residents have ILI or ARI; this includes appropriate PPE use and placement in a single-person room when examining a patient with known or suspected respiratory infection.
TBP should be based on the clinical syndrome and the likely etiologic agents (e.g., which respiratory viruses are circulating in the community, contact with someone known to have a specific respiratory viral infection) and modified once the pathogen is identified or a transmissible infectious etiology is ruled out.
If the etiology is uncertain and SARS-CoV-2 is considered possible, follow TBP recommendations specified for SARS-CoV-2 until this diagnosis has been excluded.
If pathogen-specific testing is performed and is negative, consider continuation of TBP according to isolation precautions guidelines until infectious etiology has been ruled out, the patient/resident has demonstrated sufficient improvement according to facility policy, or as directed by public health.
This page aims to provide a comprehensive set of interventions for preventing the transmission of viral respiratory pathogens in nursing homes. Its contents may be adapted for use in other long-term care settings.
This guideline by the Infectious Diseases Society of America (IDSA) includes considerations for evaluating fever and infection among a distinct subset of patients: older adults in long-term care facilities.
On this page, CDC publishes respiratory virus activity levels by jurisdiction, including for specific conditions (e.g., COVID-19, Influenza, RSV) and acute respiratory illness (ARI).
This page indexes several resources useful to the investigation of unexplained respiratory disease outbreaks, including tools for generating a differential diagnosis, infection control recommendations, and guidance for specific pathogens.
This page serves as an index to CDC’s Yellow Book, which includes health guidance and recommendations for international travelers and their healthcare providers. Yellow Book includes guidance for post-travel evaluation of respiratory infections.
