Click here to view the IMAC influenza disease factsheet.

Influenza (flu) is a common viral illness. Most cases occur during the winter months: May to October in New Zealand. It is easily spread to others through talking, coughing and sneezing. People are at risk of repeatedly catching influenza because the virus types or strains are constantly changing.


Most people who develop influenza will recover, but some cases can lead to serious complications or even death. People who are highest risk of influenza complications include the very young, those aged over 65 years, those with weakened immune systems and women who are pregnant - however serious complications can occur at any age.

The bacterium Haemophilus influenzae was thought to be the cause until the influenza-A virus was identified in 1933 confirming them as two separate diseases. Influenza vaccines were first used in the community from the late 1930s.

In 2009, a pandemic influenza-A H1N1 virus spread around the world. This influenza-A virus had undergone a change, called an antigenic shift, creating the pandemic strain. Many people, particularly those under 65 years of age did not have any immunity to this virus. Influenza related hospitalisations are usually less than 500 per year in New Zealand, but in 2009, there were about 1,500 hospitalisations related to the A/H1N1 pandemic influenza strain, and 49 people died.

The website provides information and answers frequently asked questions about influenza.


People catch influenza by breathing in virus-containing droplets that have been talked, laughed, sneezed or coughed into the air by a person with the disease or, by touching their mouth, nose or eyes after touching something that the infected droplets have recently landed on. The virus survives outside the body for a short while.


Influenza illness can include any or all of the following symptoms:

  • Fever
  • Muscle or body aches
  • Headache
  • Lack of energy,- may be severe and last for two or more weeks
  • Dry cough
  • Sore throat
  • Runny nose
  • Vomiting and diarrhoea - more common in children than in adults.

Influenza is not just a 'bad cold'. Although some of the symptoms are the same, influenza is usually much more severe, often has a sudden onset and can have much more serious consequences.


If identified early, antiviral medication can shorten how long the illness lasts, make the symptoms less severe and/or prevent serious complications.

Symptoms can be managed using medications that relieve fever and pain. Review by a doctor is very important if the person has an existing medical condition, difficulty breathing, pain or pressure in the chest, dizziness, confusion, severe or prolonged vomiting, or if they start getting better then get worse.


Influenza can lead to serious complications and death, particularly for pregnant women and in people with existing medical conditions, such as heart or lung conditions. Complications can include sinus infection, ear infection, bronchitis, pneumonia, heart failure, worsening asthma and miscarriage.

View our factsheets for more detailed information on the impact of influenza for older people, children and during pregnancy.


Annual immunisation prior to or during the influenza season is recommended for everyone who can be vaccinated. The vaccine is funded for all pregnant women, people from 65 years and certain at-risk groups from six months to 65 years. Many employers offer the vaccine to their staff.

Following basic hygiene practices can reduce spread of the virus:

  • Wash and dry hands thoroughly or use hand sanitiser before touching your mouth, nose or eyes
  • Use disposable tissues. One blow and throw the tissue away, preferably into a rubbish bin with a lid or a plastic liner, then wash and dry hands, or use hand sanitiser
  • Cover coughs and sneezes with a disposable tissue or, if no tissues are available, cough or sneeze into the inside of your elbow or arm
  • Regularly clean flat surfaces, door handles, bathroom sinks and taps
  • Stay at home if you are sick
  • Keeping at least one metre away from people who you know are sick helps reduce the spread of influenza. Keeping at least two metres away from anyone who is not in your bubble helps reduce the spread of influenza.
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