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Seasonal influenza: guidance, data and analysis

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

Published 14 July 2014
Last updated 2 August 2017 — see all updates

• From: Public Health England

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.

Management and treatment

• Amantadine, oseltamivir and zanamivir (Relenza) for the treatment of influenza National Institute for Health and Clinical Excellence (NICE) technology appraisal 168, February 2009.

• Oseltamivir, amantadine (review) and zanamivir for the prophylaxis of influenza NICE technology appraisal 158, September 2008.

1. Seasonal influenza: managing cases in critical care units
   • 28 July 2017
   • Guidance
2. Influenza: treatment and prophylaxis using anti-viral agents
   • 10 October 2017
   • Guidance
3. Respiratory tract infections: infection control
   • 2 November 2016
   • Guidance
4. Influenza-like illness (ILI): managing outbreaks in care homes
   • 11 December 2017
   • Guidance
5. Acute respiratory infections: investigating outbreaks and clusters in schools
   • 1 November 2010
   • Guidance

Epidemiology

National and international partners work with PHE to track influenza’s spread and effect on health worldwide:

• Health Protection Scotland: respiratory infections
• Public Health Agency, Northern Ireland: seasonal influenza
• Public Health Wales: weekly flu activity in Wales
• European influenza surveillance network
• World Health Organization: seasonal influenza

1. Weekly national flu reports: 2017 to 2018 season
   • 13 September 2018
   • Official Statistics
2. Annual flu reports
   • 24 May 2018
   • Official Statistics
3. Sources of UK flu data: influenza surveillance in the UK
   • 24 September 2018
   • Guidance

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.

1. Referring influenza samples to respiratory virus unit, PHE Colindale
   • 25 August 2017
   • Guidance

Antiviral resistance

1. Influenza: antiviral susceptibility surveillance and diagnosis of resistance
   • 2 December 2016
   • Guidance

Data submission

The winter health watch summarises findings from the surveillance systems that track reported flu, norovirus, and rotavirus levels, and syndromic surveillance findings through the winter season.

1. Acute respiratory infection outbreak: reporting form
   • 18 July 2018
   • Form

Published 14 July 2014
Last updated 2 August 2017 + show all updates

1. 2 August 2017 Added 'Seasonal influenza: managing cases in critical care units' under management and treatment section.
2. 9 February 2016 Web link added for seasonal influenza risk assessment (2015-2016) for countries in the EU/EEA.
3. 14 July 2014 First published.