The main goal of emerging respiratory virus surveillance is early detection of any case in Canada. Subsequently, such virus surveillance informs efforts at containment and/or mitigation of this novel respiratory pathogen. This document outlines surveillance case definitions for Avian Influenza A(H7N9) Virus and provides instructions on reporting to the national level. More detailed information on surveillance guidelines, including recommendations for surveillance objectives, activities, laboratory testing, and reporting of results, are described in the National Surveillance Guidelines for Human Infection with Avian Influenza A(H7N9).
Surveillance case definitions are provided here for the purpose of case classification and reporting to the Public Health Agency of Canada. They are based on the current level of epidemiological evidence and uncertainty, and public health response goals. These surveillance case definitions are not intended to replace clinician or public health practitioner judgment in individual patient management, or intended to be used for the purpose of infection control triage.
It should be noted that unusual severe acute respiratory illness (SARI) clusters in community or facility settings (and notably involving health care workers) should be appropriately investigated under the direction of local and provincial health authorities.
Initial screening tests specific for Avian Influenza A(H7N9) can be performed in select laboratories (i.e. provincial public health and hospital-based laboratories); however, confirmation of diagnosis should be sought from Canada's National Microbiology Laboratory (NML) before being considered conclusive. Such cases are considered probable pending NML confirmation. For more information on appropriate specimens or targets for laboratory testing, refer to the Protocol for Microbiological Investigations of Severe Acute Respiratory Infections (SARI).
Provincial/Territorial public health authorities should report confirmed and probable cases of H7N9 nationally within 24 hours of their own notification. National surveillance case definitions are provided below - these are subject to change with ongoing monitoring and as understanding of H7N9 characteristics and risk assessments evolve.
Person under investigation (PUI):
Note: The surveillance mechanisms and systems for identifying a PUI may vary by jurisdiction according to perceived risk, resources, supporting structures and other context.
Note: Limited data suggest that H7N9 can present as a co-infection with other viral as well as bacterial pathogens. The identification of one causal agent should not exclude H7N9 where the index of suspicion may be high.
Many infectious diseases present with a spectrum of illness, including mild or asymptomatic infection. Atypical H7N9 presentation with absent respiratory symptoms has been documented in the presence of comorbidity, notably immuno-suppression. Therefore, clinician and public health judgment should be used in assessing patients with milder or atypical presentations, where, based on contact, comorbidity or cluster history, the index of suspicion may be raised. Additional information can be found in the Interim Guidance For Containment When Imported Cases With Limited Human-To-Human Transmission Are Suspected/Confirmed In Canada.
Clinician discretion, epidemiologic context and local feasibility should be taken into account in discussion with local/provincial health authorities.