Current case definition for zoonotic influenza in humans

This is the case definition for zoonotic influenza, as published in the Official Journal of the European Union (Commission Implementing Decision (EU) 2018/945).

Influenza A/H5N1

Clinical Criteria

Any person with one of the following two:

— Fever AND signs and symptoms of acute respiratory infection;

— Death from an unexplained acute respiratory illness.

Laboratory Criteria

At least one of the following three:

— Isolation of influenza A/H5N1 from a clinical specimen;

— Detection of influenza A/H5 nucleic acid in a clinical specimen;

— Influenza A/H5 specific antibody response (four-fold or greater rise or single high titre).

Epidemiological Criteria

At least one of the following four:

— Human to human transmission by having been in close contact (within 1 metre) to a person reported as probable or confirmed case;

— Laboratory exposure: where there is a potential exposure to influenza A/H5N1;

— Close contact (within 1 metre) with an animal with confirmed A/H5N1 infection other than poultry or wild birds (for example, cat or pig);

— Reside in or have visited an area where influenza A/H5N1 is currently suspected or confirmed AND at least one of the following two:

— Having been in close contact (within 1 metre) with sick or dead domestic poultry or wild birds in the affected area;

— Having been in a home or a farm where sick or dead domestic poultry have been reported in the previous month in the affected area.

Case Classification

A. Possible case

    Any person meeting the clinical and the epidemiological criteria

B. Probable case

    Any person with a positive test for influenza A/H5 or A/H5N1 performed by a laboratory which is not a National Reference Laboratory participating in the EU Community Network of Reference Laboratories for human influenza (CNRL)

C. Nationally confirmed case

    Any person with a positive test for influenza A/H5 or A/H5N1 performed by a National Reference Laboratory participating in the EU Community Network of Reference Laboratories for human influenza (CNRL)

D. WHO confirmed case

     Any person with a laboratory confirmation by a WHO Collaborating Centre for H5