Influenza (Flu)

Influenza, more commonly known as the flu, is a contagious viral infection affecting around 1 in 4 New Zealanders each year.

Also known as: Flu


  • Influenza, more commonly known as the flu, is a contagious viral infection.

  • It’s very common, affecting around 1 in 4 New Zealanders each year. Around 80% of these people won’t be symptomatic, but can still spread the illness to others.

  • The flu affects a person’s sinuses, throat and sometimes lungs. Because of these symptoms, it’s often confused with the common cold, but the flu is more severe.

  • Most people who catch the flu will get better in a week or two. 

  • Those at high risk of complications from the flu include pregnant people, babies and young children, older adults and the elderly, people with obesity and those with ongoing health problems. In these people the flu can become a life threatening illness.

  • There are lots of different strains of influenza and they change constantly. It’s possible to catch more than one variant.

  • The best way to protect yourself against the flu is to get a vaccine every autumn.

  • Annual vaccines protect people against the most common strains of influenza around that year.

  • COVID-19 and the flu share some common respiratory symptoms. If you have any flu symptoms, you should also be  tested for COVID-19. Get in touch with a doctor or call Healthline’s COVID-19 number 0800 358 5453 to find out your next steps.

  • The COVID-19 vaccine is not the same as the annual flu vaccine. We recommend getting both.

What causes the flu?

  • Influenza is caused by a virus.

  • It’s spread by droplets, meaning that when an infected person sneezes or coughs, those droplets disperse in the air and can then be breathed in by others.

  • Those droplets can also land on surfaces. The illness is then spread by people touching the surface and then their face. 

  • While influenza can survive on a surface for up to a week, it normally dies within a day.

Flu symptoms in adults

  • Some people may have vomiting and diarrhea, though this is more common in children than adults.

  • Sore or scratchy throat

  • Runny or blocked nose

  • Headaches

  • Body aches 

  • Fever with temperatures over 38ºC

Flu treatments in adults

  • Most adults just need to rest, stay hydrated and let the virus run its course. You should stay home and avoid contact with other people unless seeking medical care.

  • Tea, coffee and alcohol should be avoided as they can make dehydration worse.

  • Sticking to light meals and only eating when hungry is recommended.

  • Making sure bedding is clean and dry is important. That means bedding should be changed if the patient has been sweating a lot.

  • Over-the-counter medicines can be used to help relieve symptoms.

Flu symptoms in children

  • Paracetamol may be given to children to relieve pain and fever.

  • Symptoms in children are likely to be the same as in adults. However, they may also have:  

    • Drowsiness

    • Extreme irritability 

    • Dehydration – dry nappies and a lack of tears when crying are telltale signs of dehydration in kids

    • A pale complexion

    • Short breath or wheezing

Flu medication

  • Antiviral medications like Tamiflu and Relenza can be used to treat the flu, but these are normally only prescribed when people are at risk of developing complications.

  • Unless these medicines are taken within the first 48 hours of symptoms appearing, they’re unlikely to improve the sickness any faster than bed rest.

  • Antibiotics can’t be used to treat the flu, because influenza is caused by a virus, not bacteria.

Common over-the-counter medications

  • Paracetamol and/or ibuprofen are known to help with symptoms such as bodyaches and fever.

  • Lozenges and gargles may be used to relieve sore throats.

  • Decongestants can be used to help relieve blocked sinuses and runny noses. These include nasal sprays, tablets, mentholated rubs and syrups.

  • Many over-the-counter medications shouldn’t be given to children. Be sure to read the label properly or talk to the pharmacist or your GP before giving anything to a child.

  • Aspirin should never be given to children under the age of 16.

How long does influenza last?

  • Usually about 1–2 weeks, however some symptoms like a cough may last a little longer.

  • Energy levels may also take a bit longer to recover completely.

Should I see a doctor?

You should see a doctor if: 

  • You’re not feeling any better after 4 days, or your symptoms have gotten worse.

  • You have a fever and are experiencing chills.

  • You’re having trouble breathing.

  • You have chest pain.

  • Your extremities (lips, fingers or toes) have turned a bit blue or purple.

  • You’re having seizures.

  • You’re pregnant, have recently had a baby, are over 65 years old, or have ongoing health problems.

In children:

  • Fast breathing or trouble breathing

  • Bluish lips or face

  • Ribs pulling in with each breath

  • Chest pain

  • Severe muscle pain (child refuses to walk)

  • Dehydration (no urine for 8 hours, dry mouth, no tears when crying)

  • Not alert or interacting when awake

  • Seizures

  • In children less than 12 weeks, any fever

  • Your child is presenting other symptoms that could be linked to meningococcal disease. These include: 

    • Having a stiff neck 

    • Being sensitive to bright lights 

    • Confusion or disorientation 

    • Red or purple spots appear on their skin 

    • Bruises appear on their skin

    • They refuse to eat or feed

    • Their crying sounds different 

Meningococcal disease can look a bit like the flu at first, but it worsens quickly. It’s a bacterial infection that can be treated with antibiotics but it’s really important that treatment happens early on, otherwise complications can occur.

Proactive protection

  • The best way to safeguard yourself against the flu is to get a vaccination every autumn. Each year, the vaccination will be different, depending on the most common influenza strains around at the time.

  • Wash your hands and cough into your elbowInfluenza is spread by droplets, so washing your hands with warm water and soap for 20 seconds can significantly reduce the risk of catching it. You should wash and dry your hands thoroughly before touching food, after sneezing, coughing or blowing your nose, and after touching public surfaces.

  • Carrying an alcohol-based hand sanitiser around with you is also a good way to keep your hands clean and prevent the spread.

  • Try to avoid touching your face unless completely necessary. 

  • Wear a face mask in public spaces where you may be in close contact with strangers.

  • Use alcohol-based cleaning products to wipe down surfaces in your home and workplace regularly.

Flu symptoms? Tend doctors can help

If you have flu symptoms and would like medical advice without needing to leave the house, you can book an online appointment with a Tend doctor through your app.

After the appointment, your doctor may advise that an additional, in-person appointment is required, to ensure you receive complete care. In some cases, we may require this before administering a prescription.

If this is the case, we'll book you for an in-person appointment at a time that suits you, at no extra charge.

Clinically reviewed by: Dr Mataroria Lyndon
Date of review: 5th August 2021