Views in this article should not replace medical advice. If you have symptoms of a respiratory infection, please speak to and follow the advice of a healthcare professional.
Influenza is a highly contagious respiratory illness caused by the influenza virus.1 It is one of the most common infectious diseases and represents a serious threat to public health.1 In fact, influenza causes up to 650,000 deaths around the world and is responsible for up to five million cases of severe disease every year.1 The time from infection to influenza, the incubation period, is approximately two days, but can range between one and four.1
Recognising how the influenza virus can impact your life is important in today’s busy world, especially if you have many people depending on you – your partner, children or your colleagues. Unfortunately, having influenza means you may be unable to carry out your normal daily activities for some time. 2,3
Influenza is a viral infection that causes characteristic symptoms, which can help you identify it early and seek medical advice.1
It is important that you do not underestimate the severity of influenza.4
Influenza symptoms appear suddenly, usually within one to two days of infection.5
Fever and associated symptoms last between three to eight days.5
You can feel unwell even after the fever has resolved and this can last for up to two weeks.1,5
An influenza infection can range from mild to severe illness, and some symptoms can lead to secondary complications.1,6 Without timely, appropriate treatment, influenza can lead to pneumonia, bronchitis and sinus infections.6 Although influenza is usually mild-to-moderate in the majority of those infected, for some people who are considered high-risk, severe illness and even death can occur.7
It is not just the elderly or frail who can catch influenza – people of all ages can be affected. However, some people are at higher risk of complications:1,6
Adults over 65 years
People with certain chronic medical conditions (such as asthma, diabetes, heart disease or those who have weakened immune systems)
Children under five years of age
When it comes to work, coming down with influenza can put you in a dilemma. On one hand, you may want to “tough it out” so you can meet deadlines, not let work colleagues down or allow productivity to suffer. However, going into work when you suspect that you may have influenza may not be such a good idea.
Influenza is highly contagious from the day before symptoms develop, and for up to five to seven days after you become sick.5,6
You will need to avoid contact with others, especially anyone who could be considered high-risk.1,6
You should stay at home for at least four to five days after the onset of symptoms.8
The more people you interact with, the more the infection will spread.7
It can take up to six days after you start displaying symptoms before you feel able to return to work and going into work when you have influenza puts others at risk of catching the virus too.1,8 Influenza can therefore have a considerable financial impact on those infected through days lost at work and productivity.1,2
If you could be considered at high-risk of influenza it is important to seek medical advice, as soon as you realise you have symptoms of influenza, in order to shorten the duration and impact of your illness.1,9 Due to the similarity in symptoms between some respiratory viruses, including COVID-19 and influenza, testing to determine which infection you might have is available from your healthcare professional in some settings.10,11 Getting tested early, especially for people who could be considered high-risk, will help you and your healthcare professional make informed decisions, including about potential treatment options.9
Want to find out more about influenza?
WHO 2018. Influenza (Seasonal). [Internet; cited March 2023]. Available at:
Keech M, Beardsworth P. Pharmacoeconomics. 2008;26:911–24.
Zumofen, MH.B., Frimpter, J. & Hansen, S.A. PharmacoEconomics. 2023:41:253–273.
GBD 2017 Influenza Collaborators. Lancet Respir Med. 2019 Jan;7(1):69-89.
Paules C, Subbarao K. Influenza. Lancet. 2017;390:697–708.
Centers for Disease Control and Prevention. Key Facts About Influenza (flu). [Internet; cited March 2023]. Available from:
Klepser ME. Drugs. 2014;74:1467–79.
Centers for Disease Control and Prevention. Influenza. Stay Home When You Are Sick. [Internet; cited March 2023]. Available from:
Centers for Disease Control and Prevention. Influenza Antiviral Medications: Summary for Clinicians. [Internet; cited March 2023]. Available from:
WHO. WHO Policy Brief: COVID-19 Testing. [Internet; cited March 2023]. Available from:
Centers for Disease Control and Prevention. Flu Symptoms and Complications. [Internet; cited March 2023]. Available from:
Updated May 2023
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