INFLUENZA
(influenza virus)

Clinical Criteria
Any person with at least one of the following clinical forms:
Influenza-like illness (ILI)
– Sudden onset of symptoms
AND
– at least one of the following four systemic symptoms:
– Fever or feverishness
– Malaise
– Headache
– Myalgia
AND
– At least one of the following three respiratory symptoms:
– Cough
– Sore throat
– Shortness of breath
Acute respiratory infection (ARI)
– Sudden onset of symptoms
AND
– At least one of the following four respiratory symptoms:
– Cough
– Sore throat
– Shortness of breath
– Coryza
AND
– A clinician’s judgement that the illness is due to an infection

Laboratory Criteria
At least one the following four:
– Isolation of influenza virus from a clinical specimen
– Detection of influenza virus nucleic acid in a clinical specimen
– Identification of influenza virus antigen by DFA test in a clinical specimen
– Influenza specific antibody response
Sub typing of the influenza isolate should be performed, if possible

Epidemiological Criteria
An epidemiological link by human to human transmission

Case Classification
A. Possible case
Any person meeting the clinical criteria (ILI or ARI)
B. Probable case
Any person meeting the clinical criteria (ILI or ARI) and with an epidemiological link
C. Confirmed case
Any person meeting the clinical (ILI or ARI) and the laboratory criteria