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Flu – symptoms, treatment, vaccination

Influenza (the flu) is a viral infection of the respiratory tract that spreads easily and quickly from person to person. Symptoms include fever, muscle aches and pains, and tiredness. Treatment for flu is mainly to lessen symptoms and provide comfort. Vaccination is the best means of prevention. People with immature or weakened immune systems are at a higher risk of developing serious complications from flu, such as pneumonia and bronchitis.

In New Zealand, approximately one in four people are infected with flu each year.  Although many of these people will not develop symptoms, they can still pass on the flu to other people, which is why vaccination is important.    

What is flu?

The flu is an infectious disease of the respiratory tract – the nose, throat, and lungs.  Flu is caused by different strains (variations) of influenza viruses.  The main virus strains undergo genetic change (mutation) allowing them to evade our immune systems, which is why people need to get a new vaccination every year to have immunity. The annual flu strains that circulate every winter generally do not cause widespread illness. Sometimes, however, flu outbreaks occur in which many people are affected at the same time. These outbreaks are called epidemics if they occur in one location; while worldwide outbreaks are called pandemics.

What is the difference between a cold and flu?

Colds and flu are both respiratory diseases and share some of the same symptoms (e.g. coughing, sore throat, runny nose) so it can be difficult to tell the difference. The main distinction is that flu is a more serious illness, resulting in symptoms being felt with greater intensity and carrying greater risk of serious complications and sometimes death.   Duration of the illness is a further point of difference: cold symptoms can make you feel ill for a few days, while flu symptoms can make you feel unwell for a few days to two weeks.  And, unlike flu, there is no vaccine to protect against the common cold and no anti-viral drugs have been developed to effectively treat the common cold.

Symptoms and diagnosis

Symptoms of flu, which can come on suddenly, include the following:   

  • Fever and chills
  • Cough, sore throat, and a runny or stuffy nose
  • Headache
  • Body aches and pain
  • Weakness and tiredness, sometimes severe
  • Irritated watering eyes.

Nausea, vomiting, and diarrhoea may also occur during a flu infection, especially in children. The majority of people who get the flu have symptoms for one to two weeks and then recover without any problems. However, people with weakened immune systems can develop serious and potentially life-threatening complications, such as pneumonia and bronchitis.

Diagnosis of flu is based on symptoms and a person’s association with other people known to have the disease. A rapid diagnostic test, by taking a swab sample from the upper part of the throat, can be done in a doctor’s office to determine the particular influenza strain.


Treatment for flu is mainly focused on alleviating symptoms and making the person as comfortable as possible. This includes getting plenty of bed rest at home (away from other people) and drinking plenty of fluids, using a damp cloth on the forehead to reduce fever, and taking paracetamol to relieve muscle aches and fever.

People at higher risk - the elderly, young children, pregnant women, and those with existing chronic medical conditions (including asthma, diabetes, and kidney disease) - should see their doctor early, to find out if they need treatment.  Antiviral drugs are available on prescription to reduce the severity of symptoms and prevent complications. They work best when taken within the first two days of symptoms appearing. 

Medical advice should also be sought early if you have concerns that the illness could be a more serious condition, such as meningococcal meningitis which is similar to flu in its early stages.


The illness and death caused by seasonal influenza can be prevented by getting an annual influenza vaccination (the ‘flu jab’). Seasonal vaccination is especially recommended for those people who are in an at-risk group.

If you develop flu symptoms you should follow basic hygiene practices to avoid spreading the disease to other people, including:

  • Washing your hands regularly and thoroughly or use an alcohol-based hand rub
  • Avoiding touching your eyes, nose, and mouth
  • Not sharing eating or drinking utensils
  • Staying away from work or school for as long as you have symptoms.

Further information

Freephone (24 hours): 0800 611 116

National Influenza Specialist Group
Phone: (09) 373 7599


Centers for Disease Control and Prevention (2016). Cold versus flu (Web Page). Atlanta, GA: Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases. [Accessed 27/01/18]
Immunisation Advisory Centre (Year not stated). Flu can be anywhere (Brochure). Auckland: Immunisation Advisory Centre.
Ministry of Health (2017). Influenza (Web Page). Wellington: New Zealand Government Ministry of Health. [Accessed 27/01/18]
Nguyen, H.H. (2018). Influenza (Web Page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. [Accessed: 27/01/18]
O’Toole, M.T. (Ed.) (2013). Influenza. Mosby’s Dictionary of Medicine, Nursing & Health Professions (9th ed.). St Louis. MI: Elsevier Mosby.

Reviewed: January 2018

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