Flu (influenza)

What is influenza (flu)?

Influenza, commonly called the flu, is a serious viral illness that is sometimes fatal. Anyone can catch it, no matter how fit, active and healthy they may be. 

Flu can cause any or all of these symptoms: fever, muscle aches, headache, lack of energy, dry cough, sore throat, and possibly a runny nose. The fever and body aches can last 3-5 days and the cough and lack of energy may last for 2 or more weeks. 

When should I visit a doctor if I think I have flu?

These people should see their doctor as soon as they think they have flu:

  • pregnant women
  • children and adults with long term health conditions 
  • adults aged 65 years or older.

Phone your doctor or Healthline 0800 611 116 if you think you might have flu. Stay at home if you are sick.

Call your doctor first to make an appointment. 

Visit the Health Navigator NZ flu webpage for more information about when infants, children and adults with flu should visit a doctor. 

Other people may be able to manage their flu symptoms without visiting their doctor. However, people who are worried about how serious their symptoms are, people who haven't improved after 2 weeks and those who were starting to feel better and then suddenly feel worse or develop a new symptom should also visit their doctor.

What's the difference between a cold & flu?

Flu is different from a common cold.  A cold virus only affects the nose, throat and the upper chest and lasts for a few days. Flu can be a serious illness that affects the whole body and can last for a week or longer.

Flu A comon cold
Sudden onset of illness
Moderate to severe illness
Mild illness
Fever (usually high) Mild fever
Headache (may be severe) Mild headache (congested sinuses)
Sore throat May have a sore throat
Runny or stuffy nose Runny or stuffy nose
Dry cough, may become moist Sometimes a cough
Muscle aches Muscle aches are uncommon
Chills, shivering  
Stomach upset, vomiting or diarrhoea  
Can suffer severe complications (eg pneumonia)  

How is flu spread? 

  • Around four out of five people with flu have no symptoms and don't know they can be spreading the virus to other people.   
  • Being immunised can stop you from accidently giving flu to your family, friends and other people you meet. You can reduce the spread of flu to those who may not respond quite as well to the vaccine themselves, giving them extra protection.
  • Children are major spreaders of flu and can become so unwell that they may need to go to hospital. By giving flu vaccine to your children from 6 months of age, you can protect them and your family, including their baby sisters or brothers, aunties and uncles and grandparents.

Flu can spread easily around workplaces. Encourage your employer to provide flu vaccination and take up the offer of a flu vaccine if already given at work. It can reduce the number of days you need to take off-sick, which is good for business and your colleagues.

How do I catch flu?

Flu is spread by coughing, sneezing, shouting, singing and even speaking. These droplets may land on you or on surfaces that you or others touch. Touching your face, mouth or eyes can pass the infection to you or from your hands to others.

  • By direct contact with an infected person – shaking hands, kissing
  • From moisture droplets spread by coughing and sneezing landing on you 
  • Or you touching a contaminated surface (including your own body) and then touching your mouth, nose or eyes 

You can be infectious around a day before symptoms appear. Some people don’t have symptoms but can still pass their flu onto other people.

We cannot predict from year to year how severe the flu season may be. The flu virus can change yearly and new strains can emerge to which people are not immune.

You can stop the spread of flu 

  1. Getting an annual flu vaccine is the best way for you to stop flu spreading.  
  2. If you’re unwell, stay at home until you are better.
  3. Follow basic hygiene practices.
    • Wash your hands regularly for at least 20 seconds and dry them for 20 seconds – or use an alcohol-based hand rub.
    • Cover your mouth and nose with a tissue when you cough or sneeze OR if you don’t have a tissue then cough or sneeze into your elbow. 
    • Wash your hands after blowing your nose or coughing.
    • Avoid touching your eyes, nose and mouth.
    • Don’t share drinks.
    • Avoid crowded places or wear a mask.