Influenza (the flu) is caused by a virus. Symptoms include high fever, sore throat, weakness, headache, muscle and joint pains and a cough. Treatment includes bed rest and drinking plenty of fluids. Vulnerable people are more likely to develop serious complications including pneumonia. Immunisation can offer protection from flu.
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 – influenza A, B and C. Older people, pregnant women and those with an underlying medical condition are more likely to develop serious complications as a result of the flu. These complications include secondary bacterial pneumonia, primary influenza pneumonia and inflammation of the brain and heart.
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
- General muscle and joint pains (in the legs and back)
- A non-productive (dry) cough that can later become more severe and productive (sputum or mucous is coughed up).
Flu versus the common cold
The flu is more severe than a bad cold because:
- Cold symptoms last from two to a few 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.
Complications from flu
Complications are more common among people with an underlying medical condition or reduced immunity. Flu can increase the risk of death or the risk of 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 or yellow phlegm (mucous), chest pains and a temperature. Death rates are high, but it is less lethal than primary influenza pneumonia.
- Primary influenza pneumonia – symptoms include difficulty with breathing and blue discoloration of the skin (cyanosis).
- Inflammation of the brain or heart – can occur during recovery from the flu.
- Reye’s syndrome – this 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 from flu
People with an underlying medical condition or reduced immunity are most at risk. They include:
- Anyone aged 65 years and older
- Pregnant women (at any stage of pregnancy)
- Aboriginal and Torres Strait Islander people aged 15 years and over
- Anyone aged six months or older with heart disease, chronic lung disease, chronic neurological conditions, impaired immunity and other chronic illnesses such as diabetes, kidney disease and haemoglobinopathies (blood disorders due to genetic defects in haemoglobin)
- Residents in nursing homes or other long-term care facilities
- Homeless people
- Severe asthmatics who require frequent hospital visits
- Children on long-term aspirin therapy
- Other chronic illnesses requiring regular medical follow-up or hospitalisation.
Exposure to a risk of influenza
It is recommended that people who work with or live in close contact with people who have an underlying medical condition or reduced immunity be vaccinated. This is to avoid spreading the virus and to protect themselves and their family.
Such people 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 65 years or older
- Carers of homeless people.
- 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 to:
- Stay in bed and rest until your body temperature is in the normal range 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. Discuss treatment with your doctor.
- Avoid exposure to dust, alcohol, fumes and tobacco smoke as much as possible.
It is important to take the steps outlined above 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, pregnant women, those at risk and those who work or live with these vulnerable groups. It is important to be immunised as this can help you 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 people and at risk groups should be immunised every year against the flu.
- After immunisation, protection from the flu takes 10 to 14 days to develop.
You might also be interested in:
- Coughing and wheezing in children.
- Flu (influenza) - immunisation.
- Infections - bacterial and viral.
- Pain management - children.
- Pneumococcal disease.
- Pneumococcal disease - immunisation.
- Respiratory system.
- Swine flu.
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Last reviewed: October 2012
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