Influenza infection is characterised by upper and lower respiratory tract symptoms of rhinorrhoea, cough, fever, chills, headache, and myalgia.
Typically presents in winter season.
Can occur in local community outbreaks, epidemics, and, rarely, pandemics.
Vaccination for prevention is available.
Acute respiratory tract infection typically caused by seasonal influenza A or B virus. The virus is transmitted by inhalation of infected respiratory secretions that have been aerosolised through coughing, sneezing, or talking.
History and exam
Key diagnostic factors
- winter season
- current influenza outbreak
- fever with cough
Other diagnostic factors
- sore throat
- cervical lymphadenopathy
- age ≥65 years
- age 6-59 months
- chronic cardiovascular or respiratory conditions
- chronic kidney disease (CKD)
- carers and household contacts of high-risk groups
- healthcare workers
1st investigations to order
- clinical diagnosis
Investigations to consider
- molecular assays
- antigen detection tests
- viral culture
- chest x-ray
exposure to influenza in at-risk populations
- Coronavirus disease 2019 (COVID-19)
- Bacterial pneumonia
- Rhinovirus infection
- Recommendations for obstetric health care providers related to use of antiviral medications in the treatment and prevention of influenza
- Prevention and control of seasonal influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices - United States, 2022-23 influenza season
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