Case Definitions for Infection with Novel Influenza A (H1N1) Virus

A confirmed case of novel influenza A (H1N1) virus infection is defined as a person with an influenza-like illness with laboratory confirmed novel influenza A (H1N1) virus infection by one or more of the following tests:

• real-time RT-PCR
• viral culture

Medical care for patients with novel influenza A (H1N1) virus

Not all patients with suspected novel influenza (H1N1) infection need to be seen by a health care provider.For most people, the illness appears to be mild and self-limiting. Cases have been confirmed in all age groups, but children and younger people seem to be much more likely to be affected, whereas fewer cases have been confirmed to date in older adults.

For a minority of people, influenza A(H1N1) has caused severe illness with complications. In many, but not all, of these cases underlying risk factors (co-morbidities # ) have been identified that are likely to have contributed to the severity of the condition.

Complications of Influenza:

The following are the recognized complications of influenza. At times these complications, such as an exacerbation of chronic airways disease, may be the presenting symptom. Respiratory complications are the most common ones (especially secondary infections). Cardiac events following influenza are not uncommon.

Complications of influenza	Major clinical category
Respiratory	Pneumonia: primary viral, secondary bacterial, combined Upper respiratory: otitis media, sinusitis, conjunctivitis Acute laryngotracheo-bronchitis (croup) Bronchiolitis Complication of pre-existing disease
Cardiovascular	Myocarditis Pericarditis
Muscular	Rhabdomyositis Rhabdomyolysis with myoglobinuria and renal failure
Neurological	Encephalitis Reye’s syndrome Guillain-Barré syndrome Transverse myelitis
Systemic	Toxic shock syndrome Sudden death

# Co-morbidities / Risk factors:

Patients who are considered vulnerable to severe outcomes and should be a focus of early identification, assessment and treatment, include the following:

• Chronic respiratory conditions, including asthma, COPD, Obstructive sleep apnoea
• Pregnant women, esp. in second or third trimester
• Morbid obesity
• Other possible predisposing conditions, such as chronic cardiac disease (not simple hypertension), and chronic illnesses including diabetes mellitus, renal failure, haemoglobinopathies, immunosuppression (including cancer, HIV/AIDS, chemotherapy, long term steroids).
• Adults > 65 years of age esp. those with other chronic diseases
• Children under the age of 5 years, esp. those below the age of 2 years

As more epidemiologic and clinical data become available, these risk groups might be revised.