Influenza or the “flu” is a viral infection that causes characteristic symptoms that can help you identify it early and seek medical advice.1,2 Influenza, or ‘flu’, is a short-lived, highly contagious, serious respiratory illness caused by a virus.3

Flu can be easily confused with other respiratory illnesses, such as the common cold because some milder symptoms are similar. Recognising the symptoms of flu early is key to effective treatment and prevention of the virus spreading.4

In general, flu is worse than the common cold, and symptoms are more intense. Also, colds generally do not result in serious health problems, such as pneumonia, bacterial infections or hospitalisations.4 Possible serious complications triggered by flu include not only pneumonia, but can also include myocarditis, encephalitis and sepsis, all of which can increase the risk of death.5

Table adapted from reference 4.
x = rare, uncommon or slight; xx = fairly common or sometimes; xxx = usual or common

Warning signs of increased severity of flu can include difficulty breathing or shortness of breath, persistent pain or dizziness, dehydration, as well as severe muscle pain and weakness.4

You can feel unwell even after the fever has resolved, and this can last for up to 2 weeks, meaning you may be unable to carry out your normal daily activities for some time.6,7

Many people think that there is little point in contacting their doctor when they have the flu. It has been shown that few people infected with flu seek medical care within the first 2 days of developing symptoms.7,8 However, if you have the flu, it can have a significant impact on your home and work life, so it is important to seek medical advice as soon as you realise you have the flu, to help to shorten the duration and impact of your illness.6,7,10

As with any airborne infectious disease, everyday preventive actions such as staying away from people who are sick, covering coughs and sneezes and frequent handwashing are always important.1

Before the onset of the flu, taking the flu vaccine can reduce the odds of becoming infected.11 However, the effectiveness of the flu vaccine depends on a number of different factors, including your age, general health, when you get the vaccine and how well matched it is to the dominant flu strains for the current season.11

It may be tempting to ask for an antibiotic to manage your viral flu infection. However, antibiotics are not an appropriate treatment as they are designed to treat bacterial infections and have no effect on viral infections.12

You may choose to use over-the-counter (OTC) medication to manage the symptoms of the flu. While OTC medication can help with reducing your fever, aches, pains and congestion they do not directly affect the course of influenza virus infection or reduce the ability to pass the infection on to others.2 If you are at risk for influenza-related complications, you should not use OTC medicines to delay seeking medical attention, but should immediately consult your doctor.2 People at high risk for complications include those ≥65 years of age, those with certain chronic medical conditions (such as asthma, diabetes or heart disease), pregnant women and children younger <5 years of age.5

There are also antiviral treatment options available to manage your flu infection. Flu antiviral drugs are not OTC medicines and you can only get them if you have a confirmed diagnosis of flu and a prescription from a doctor.13

Flu antivirals, which have been shown to not only shorten the duration of flu symptoms,14,15 can also reduce the risk of severe illness and death,2 with the greatest benefit noted when antiviral treatment is administered as soon as possible after the onset of symptoms.10

References

1. Centers for Disease Control and Prevention. Key facts about influenza (flu). Available from: https://www.cdc.gov/flu/about/keyfacts.htm. (Accessed March 2020).

2. Klepser ME. Socioeconomic impact of seasonal (epidemic) influenza and the role of over-the-counter medicines. Drugs. 2014;74:1467–79.

3. Centers for Disease Control and Prevention. About Flu. Available from: https://www.cdc.gov/flu/about/index.html. (Accessed March 2020).

4. Centers for Disease Control and Prevention. Cold versus flu. Available from: https://www.cdc.gov/flu/symptoms/coldflu.htm.

5. Centers for Disease Control and Prevention. Flu symptoms and complications. Available from: https://www.cdc.gov/flu/symptoms/symptoms.htm. (Accessed March 2020).

6. Keech M, Beardsworth P. The impact of influenza on working days lost: a review of the literature. Pharmacoeconomics. 2008;26:911–24.

7. Paules C, Subbarao K. Influenza. Lancet. 2017;390:697–708.

8. Gaglia MA, et al. Patient knowledge and attitudes about antiviral medication and vaccination for influenza in an internal medicine clinic. Clin Infect Dis. 2007;45:1182–8.

9. Biggerstaff M, et al. Influenza-like illness, the time to seek healthcare, and influenza antiviral receipt during the 2010–11 influenza season — United States. J Infect Dis. 2014; 210: 535–44.

10. Centers for Disease Control and Prevention. Influenza antiviral medications: summary for clinicians. Available from: https://www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm. (Accessed July 2019).

11. WebMD. How effective is the flu vaccine? Available from: https://www.webmd.com/vaccines/how-effective-is-flu-vaccine#1. (Accessed March 2020).

12. Imanpur S, et al. Factors associated with antibiotic prescriptions for the viral origin diseases in office-based practices, 2006–2012. JRSM Open. 2017;8(8):2054270417717668.

13. Centers for Disease Control and Prevention. What You Should Know About Flu Antiviral Drugs. Available from: https://www.cdc.gov/flu/treatment/whatyoushould.htm. (Accessed March 2020).

14. The MIST (Management of Influenza in the Southern Hemisphere Trialists) Study Group. Randomised trial of efficacy and safety of inhaled zanamivir in treatment of influenza A and B virus infections. Lancet. 1998;352:1877–81.

15. Treanor JJ, et al. Efficacy and safety of the oral neuraminidase inhibitor oseltamivir in treating acute influenza: a randomized controlled trial. JAMA. 2000;283:1016–24.

16. Kaiser L, et al. Impact of zanamivir on antibiotic use for respiratory events following acute influenza in adolescents and adults. Arch Intern Med. 2000;160:3234–40.

17. Lalezari J, et al. Zanamivir for the treatment of influenza A and B infection in high-risk patients: a pooled analysis of randomized controlled trials. Arch Intern Med. 2001;161:212–7.

18. Kaiser L, et al. Impact of oseltamivir treatment on influenza-related lower respiratory tract complications and hospitalizations. Arch Intern Med. 2003;163:1667–72.