Flu (influenza)

Influenza, commonly known as the flu, is caused by a highly contagious virus that is spread by coughs and sneezes. There are three types of flu virus – A, B and C. Older people and those with an underlying medical condition are more likely to develop serious complications as a result of the flu.

The flu virus has a unique ability to change its surface structure. This allows it to escape recognition by the body’s immune system and cause widespread illness (epidemics and pandemics). Most cases of influenza occur within a six to eight-week period during winter and spring.

Epidemics occur when there are minor changes in the nature of the virus so that more people within a community are susceptible. Influenza A is more likely to cause epidemics. Pandemics (worldwide epidemics) occur when there are major changes in the virus so that the disease affects a large proportion of people in a geographic region or on more than one continent.

Influenza epidemics occur, on average, every three years. Influenza pandemics have occurred four times in the past 100 years and can cause many deaths.

Symptoms of flu

Flu symptoms develop one to three days after infection and include:

• High fever, chills and sweating
• Sore throat
• Weakness
• Headache
• General muscle and joint pains (legs and back)
• A non-productive cough that can later become more severe and productive.

Flu versus the common cold

The flu is more than a bad cold:

• Cold symptoms last one to two days while the flu can last up to a week.
• The flu causes a high fever. A cold sometimes causes a mild fever.
• Muscular pains and shivering attacks occur with the flu, but not with a cold.
• Colds cause a runny nose, while the flu usually starts with a dry sensation in the nose and throat.

Serious complications are rare

Complications are more common among people with an underlying medical condition or reduced immunity. Flu can increase the risk of death or serious complications from the underlying disease. In a small proportion of cases, flu will lead to:

• Secondary bacterial pneumonia – occurs when bacteria invade the lungs. Symptoms include shortness of breath, green–yellow phlegm, chest pains and a temperature. Death rates are high but it is less lethal than primary influenza pneumonia.
• Primary influenza pneumonia – symptoms include difficulty breathing and blue discoloration of the skin (cyanosis).
• Inflammation of the brain or heart – can occur during recovery from the flu.
• Reye’s syndrome – leads to brain inflammation and liver degeneration and is fatal in between 10 and 40 per cent of cases. Children under 16 years should not be given any medication containing aspirin as it increases the risk of Reye’s syndrome.

People at risk of complications

People with an underlying medical condition or reduced immunity are most at risk. They include:

• Everyone aged 65 years and older
• Aboriginal and Torres Strait Islander people aged 15 years and over
• Anyone from six months of age with heart disease, chronic lung disease, chronic neurological conditions, impaired immunity and other chronic illnesses such as diabetes, kidney disease and haemoglobinopathies
• Residents in nursing homes or other long-term care facilities
• Homeless people
• Severe asthmatics who require frequent hospital visits
• Pregnant women during any stage of pregnancy
• Children on long-term aspirin therapy
• Other chronic illnesses requiring regular medical follow-up or hospitalisation.

People who can put vulnerable people at risk of infection

People who work with or live in close contact with people who have an underlying medical condition or reduced immunity are also recommended to be vaccinated to avoid spreading the virus and to protect themselves and their family. They include:

• Public and private hospital staff who provide direct care to patients
• Staff in long-term care facilities or nursing homes
• People who live with, or care for someone who has a chronic illness or is aged
• Carers of homeless people.

Other people who it is recommended be vaccinated are:

• Workers, particularly those in workplaces that provide essential services
• People who work with children
• People involved in the commercial poultry and pig industry
• Anyone travelling as part of a group.

Treatment of flu

There are now specific antiviral drugs available, but they need to be given early in the illness. The recommended treatment for mild or moderate flu is:

• Stay in bed and rest until the temperature has been normal for 48 hours.
• Drink enough fluids to maintain normal urine output.
• Take paracetamol to control fever, aches and pains (adults can use aspirin). Early use of antiviral medication may shorten the length and severity of illness. Consult a doctor to discuss treatment.
• Avoid exposure to dust, alcohol, fumes and tobacco smoke as much as possible.

Consult a doctor if further symptoms develop such as difficulty breathing, coughing up green–yellow phlegm or severe headache.

This is important to avoid serious complications, such as pneumonia, that may arise as a result of contracting the virus.

Immunisation for flu

Annual immunisation is strongly recommended for older people and those ‘at risk’. This is important to avoid serious complications, such as pneumonia, that may arise as a result of contracting the virus. Immunisation should ideally occur between March and May, before the onset of the flu season. Protection develops about two weeks after the injection and lasts for up to one year.

In Victoria, an annual flu immunisation is provided free of charge for those people in the community who are considered to be at an increased risk of developing complications. Contact your doctor or immunisation provider for further information about eligibility.

Where to get help

• Your doctor
• Nurse-on-Call Tel. 1300 60 60 24 – for expert health information and advice (24 hours, 7 days)
• Your local council
• Your local community health centre
• Immunisation Section, Department of Health Victoria Tel. 1300 882 008
• The emergency department of your nearest hospital

Things to remember

• The flu is more than just a bad cold.
• Flu can occasionally lead to serious complications including death.
• Older and ‘at risk’ groups should be immunised every year against the flu.
• Protection after immunisation takes 10 to 14 days.

You might also be interested in:

• Colds explained.
  
• Coughing and wheezing in children.
  
• Flu (influenza) - immunisation.
  
• Infections - bacterial and viral.
  
• Pain management - children.
  
• Pneumococcal disease.
  
• Pneumococcal disease - immunisation.
  
• Pneumonia.
  
• Respiratory system.
  
• Swine flu.
  

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Last reviewed: July 2011

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<a href="http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Flu_influenza?open">Flu (influenza) - Better Health Channel</a><br/>
Influenza (the flu) is caused by a virus. Flu symptoms include high fever, chills and sweating, sore throat, weakness, headache, muscle and joint pains and a cough. Treatment includes bed rest, paracetamol and drinking plenty of fluids. Immunisation can protect vulnerable people from the flu. Older people and those with an underlying medical condition are more likely to develop serious complications including secondary bacterial pneumonia, primary influenza pneumonia and inflammation of the brain or heart.

Content on this website is provided for education and information purposes only. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your qualified health professional. Content has been prepared for Victorian residence and wider Australian audiences, and was accurate at the time of publication. Readers should note that over time currency and completeness of the information may change. All users are urged to always seek advice from a qualified health care professional for diagnosis and answers to their medical questions.

For the latest updates and more information, visit www.betterhealth.vic.gov.au

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