Avian influenza A(H7N9) virus infection

Centers for Disease Control and Prevention (CDC): case definitions for investigations of human infection with avian influenza A viruses in the United States[125]Centers for Disease Control and Prevention. Case definitions for investigations of human infection with avian influenza A viruses in the United States. Mar 2022 [internet publication]. https://www.cdc.gov/flu/avianflu/case-definitions.html

Confirmed case:

• Avian influenza A virus infection in a patient that is confirmed by the CDC’s Influenza Division Laboratory or a CDC-designated laboratory using methods mutually agreed upon by the CDC and the Council of State and Territorial Epidemiologists (CSTE).

Probable case:

• A person meeting epidemiologic and clinical criteria for avian influenza A virus infection (below) and for whom confirmatory laboratory test results do not provide a sufficient level of detail to confirm infection.

Suspected case (case under investigation):

• A person meeting epidemiologic and clinical criteria for avian influenza A virus infection (below) and for whom confirmatory laboratory test results are not known or pending.

Epidemiologic criteria:

• People with recent exposure (within 10 days) to avian influenza A viruses through one of the following:

  • Exposure to A(H5), A(H7), or A(H9) virus-infected birds

  • Exposure to an infected person

  • Laboratory exposure.

Clinical criteria:

• People with signs and symptoms consistent with acute or lower respiratory tract infection or conjunctivitis, or complications of acute respiratory illness without an identified cause.

CDC: case definitions for investigations of human infection with avian influenza A viruses in the United States Opens in new window

UK Health Security Agency (UKHSA): case definition for possible cases of avian influenza with potential to cause severe human disease[126]UK Health Security Agency. Investigation and initial clinical management of possible human cases of avian influenza with potential to cause severe human disease. Nov 2021 [internet publication]. https://www.gov.uk/government/publications/avian-influenza-guidance-and-algorithms-for-managing-human-cases

Possible cases must fulfill the clinical AND exposure criteria below.

Clinical criteria:

• Fever >100.4ºF (>38ºC); or

• Acute respiratory symptoms (e.g., cough, hoarseness, nasal discharge or congestion, shortness of breath, sore throat, wheezing or sneezing); or

• Other severe or life-threatening illness that is suggestive of an infectious process.

Exposure criteria:

• Close contact (within 3 feet [1 meter]) with live, dying, or dead domestic poultry or wild birds (including live bird markets), in an area of the world affected by avian influenza, or with any confirmed infected animal, in the 10 days before the onset of symptoms; or

• Close contact with a confirmed human case of avian influenza, or human case(s) of severe unexplained respiratory illness from avian influenza affected areas, or human case(s) of unexplained illness resulting in death from avian influenza infected areas, in the 10 days before the onset of symptoms.

  • Close contact includes handling laboratory specimens from cases without appropriate precautions, within 1 meter distance, directly providing care, touching a case, or within close vicinity of an aerosol-generating procedure, from 1 day prior to symptom onset and for duration of symptoms or positive virologic detection.