Seasonal influenza: guidance, data and analysis

The symptoms, diagnosis, management, surveillance and epidemiology of seasonal influenza (flu).

Influenza (flu) is a viral infection affecting the lungs and airways. The symptoms can appear very quickly and include:

  • headache
  • fever
  • cough
  • sore throat
  • aching muscles
  • joints

Complications include bacterial pneumonia, and can be life threatening especially in:

  • older people
  • those with certain underlying health conditions

It occurs most often in winter in the UK and peaks between January and March.

There are 2 types of influenza affecting people:

  • influenza A
  • influenza B

Influenza B usually causes a milder illness, and is most seen in children.

Information on the different strains of influenza virus can be found on our health protection archive website.

Seasonal influenza risk assessment for 2015 to 2016, for countries in the EU/EEA can be downloaded from the ECDC website

Annual flu programme

Vaccination of at risk groups and children can offer some protection against infection. The NHS plans each year for the demands of flu across England in its annual flu programme.

See Latest vaccine uptake guidance and the latest coverage for figures on seasonal flu vaccination rates.

Diagnosis, management and treatment


Respiratory Virus Unit services and guidance for laboratories

The Respiratory Virus Unit (RVU) provides laboratory services for respiratory infections including influenza. Further information and guidance is available on RVU services.

Antiviral resistance

Published 14 July 2014
Last updated 17 November 2021 + show all updates
  1. Added UK Influenza Network Laboratories: interpretation of influenza-positive results.

  2. Added weekly national flu report for 2019 to 2020 season.

  3. Added 'Point of care tests for influenza and other respiratory viruses'.

  4. Added 'weekly national flu reports: 2018 to 2019 season' to the collection.

  5. Added 'Influenza-like illness (ILI): managing outbreaks in schools'.

  6. Added 'Seasonal influenza: managing cases in critical care units' under management and treatment section.

  7. Web link added for seasonal influenza risk assessment (2015-2016) for countries in the EU/EEA.

  8. First published.