Influenza

Influenza, more universally known as the flu, is common across the globe. Flu is mostly seasonal, occurring more widely in autumn and winter. Seasonal influenza is defined as:

There are a few varieties of flu, such as bird flu (also known as avian flu) and swine flu, but this article focuses on seasonal influenza or flu.

The symptoms of flu vary between individuals and according to the causative virus. However, common symptoms generally include:

• sudden onset of fever
• cough (usually dry)
• headache
• myalgia
• arthralgia
• severe malaise
• sore throat
• nasal discharge (National Institute for Health and Care Excellence (NICE), 2023; WHO, 2024)

Most cases of flu last for up to 7-10 days, although in some cases the cough can be severe and might last up to 14 days (WHO, 2024). In more severe cases, flu can lead to signs and symptoms which require hospitalisation as a result of significant lower respiratory tract infections, central nervous system involvement and/or the exacerbation of an underlying condition, such as asthma or chronic obstructive pulmonary disease (NICE, 2023).

Up to 50% of all people infected by flu are asymptomatic (UK Health Security Agency, 2023), creating challenges when trying to prevent transmission of the infection.

Flu is caused by RNA viruses from the family orthomyxoviridae (NICE, 2023), and belong to one of three types: A, B and C. Type A is the most common and virulent, while type C is the least common and virulent (UK Health Security Agency, 2023).

Types A and B may be further divided into subtypes depending on the antigens present on the virus, defined as H and N, and by antigenic subtypes, ie H1, H2, H3, N1 and N2. Small mutations on the proteins which make up the viruses cause the antigens to appear in different places on the virus and lead to the need for new flu vaccinations each year to target the most recent antigen presentations (Radojicic, 2023).

Influenza viruses are spread by droplets and aerosols produced during coughing or sneezing (Radojicic, 2023), as well as through direct contact with the respiratory secretions of an infected individual (UK

The diagnosis of flu is based on the presenting signs and symptoms of the illness in addition to the knowledge that flu is present in the community (NICE, 2023). However, laboratory testing, consisting of a nose or throat swab sent to the virology laboratory, is an option for people with complications of flu which appear not to be improving despite antiviral treatment.

Several other illnesses and infections may present in a similar way to flu, although these are most likely to occur when seasonal flu is not circulating. These include:

• common cold
• respiratory syncytial virus infection
• parainfluenza virus infection
• pertussis infection (NICE, 2023)

The annual flu vaccination programme was developed to prevent transmission and infection of the flu. NICE (2020) suggests increasing vaccine uptake, which can be achieved by several recommended methods, such as:

• using a variety of means to invite people for their flu vaccine, such as by taking a multicomponent approach to vaccination (ie offering vaccines widely in different places)
• raising awareness through education
• targeting awareness in at-risk and low uptake groups and ensuring people in at-risk groups receive information about the vaccine which relates to their condition
• taking every opportunity to offer the vaccine, eg when patients visit the practice nurse with a different complaint
• auditing provision by recording information about patients who are vaccinated
• ensuring health and social care staff who meet the public have the vaccine (NICE, 2018)

For most people, the management of flu is simply based on the management of their symptoms using mild analgesics, such

Flu can give rise to various complications including:

• acute bronchitis
• pneumonia
• exacerbations of asthma
• exacerbations of chronic obstructive pulmonary disease
• otitis media
• sinusitis (NICE, 2023)

Complications are more common in people with underlying health conditions and older people, and may require hospitalisation and management.

Nursing and Midwifery Council: standards of proficiency for registered nurses

Part 1: Procedures for assessing people’s needs for person-centred care

1. Use evidence-based, best practice approaches to take a history, observe, recognise and accurately assess people of all ages

Part 2: Procedures for the planning, provision and management of person-centred nursing care

11. Procedural competencies required for best practice, evidence-based medicines administration and optimisation

UK Health Security Agency. Influenza: the green book, chapter 19. 2023. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/931139/Green_book_chapter_19_influenza_V7_OCT_2020.pdf (accessed 29 January 2024)

National Institute for Health and Care Excellence (NICE). Amantadine, oseltamivir and zanamivir for the treatment of influenza. 2009. https://www.nice.org.uk/guidance/ta168/chapter/1-Guidance (accessed 29 January 2024)

National Institute for Health and Care Excellence (NICE). Flu vaccination: increasing uptake. 2018. https://www.nice.org.uk/guidance/ng103 (accessed 29 January 2024)

National Institute for Health and Care Excellence (NICE). Flu vaccination: increasing uptake. 2020. https://www.nice.org.uk/guidance/qs190 (accessed 29 January 2024)

National Institute for Health and Care Excellence (NICE). Influenza - seasonal. 2023. https://cks.nice.org.uk/topics/influenza-seasonal/ (accessed 29 January 2024)

Radojicic C. Influenza infection. 2023. https://bestpractice.bmj.com/topics/en-us/6 (accessed 29 January 2024)

Royal College of Nursing. RCN position on health care staff and the influenza vaccine. 2021. https://www.rcn.org.uk/about-us/our-influencing-work/position-statements/rcn-position-on-health-care-staff-and-the-influenza-vaccine (accessed 29 January 2024)

World Health Organization (WHO). Five simple steps to protect against flu. 2019. https://www.who.int/news-room/feature-stories/detail/five-simple-steps-to-protect-against-flu (accessed 29 January 2024)

World Health Organization (WHO). Influenza seasonal. 2024. https://www.who.int/health-topics/influenza-seasonal#tab=tab_1 (accessed 29 January