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Influenza

  • Influenza (or flu) is a short-term illness caused by a virus. It can affect people of any age

  • Influenza is common and outbreaks of influenza A occur most winters, with epidemics every 5 to 15 years. Influenza B causes epidemics, but less frequently. Influenza C does not appear to cause epidemics, and by the age of 15 most of the population have developed antibodies against it[i] (see below for further information on the types of influenza)
  • Flu is highly infectious and is spread from person to person, for example by sneezing. Symptoms appear one to four days after a person catches the virus
  • Infection rates for influenza are highest among school age children and decrease with age[ii]
  • Deaths and hospitalisations due to severe or complicated influenza mostly occur in infants and the elderly[iii]
  • Women have a higher mortality rate from influenza than men[iv]

  • The number of hospital admissions for influenza is fairly low, typically less than 20 a week, rising to 70-80 a week during the winter[v]

  • Flu can sometimes bring on more serious health problems when the body’s defences, particularly those in the lungs, have been weakened by the flu virus. The most common of these is pneumonia
  • Deaths certified as due to influenza have fallen since the 1960s. There are now about 250 deaths in non-epidemic years, 80-90% occurring in those aged over 65[vi]
  • Epidemics of influenza occur irregularly but the winter of 1989-90 saw quite a severe flu epidemic in the UK, causing between 20,000 and 30,000 extra deaths. About half of these deaths were due to lung disease; other causes included heart attacks, strokes and diabetes[vii]


[i] http://www.sghms.ac.uk/depts/laia

[ii] http://www.sghms.ac.uk/depts/laia/954.pdf

[iii] http://www.sghms.ac.uk/depts/laia/954.pdf

[iv] http://www.sghms.ac.uk/depts/laia/954.pdf

[v] http://www.sghms.ac.uk/depts/laia/954.pdf

[vi] http://www.sghms.ac.uk/depts/laia/954.pdf

[vii] British Lung Foundation, Flu (2005)