Lung Foundation

What is influenza?

Influenza is an infection caused by a virus. It is spread from person to person by tiny drops produced during a cough or sneeze and by hand to hand contact. While we often call the common cold the "flu", the common cold is rarely due to the Influenza virus. True influenza causes a much more severe illness than the usual cold.

What happens when you get influenza?

After infection, it takes 1-3 days for symptoms to develop. Healthy people mostly have symptoms of a sore throat, dry cough, nausea and sore eyes. Fever, chills, muscle aches and pains, loss of appetite occur in more severe cases. These symptoms usually settle after a week. You often feel very tired for days or even weeks after the flu. Some people can have life threatening complications.

When is influenza considered serious?

Influenza can be severe or even fatal if a person is not in good health to begin with. The body and its defences can also become so weakened by influenza that other infections can occur. Pneumonia, sinusitis, airway or inner ear infection may occur. Rare and sometimes fatal problems include inflammation of the brain and nervous system and kidneys. Influenza can also worsen other problems such as diabetes, chronic bronchitis or heart failure.

Who are more susceptible to the serious complications of influenza?

Health problems which make people more likely to develop the complications of influenza include:-

• Chronic lung disease including asthma, chronic bronchitis, emphysema, bronchiectasis and cystic fibrosis
• Heart disease
• Kidney disease
• Diabetes
• Severe anaemia
• Frail and elderly people living in nursing homes
• People taking corticosteriods or other drugs that reduce immunity

How are influenza and its complications treated?

Bed rest helps muscle aches and pains and paracetamol helps lower fever. Aspirin is also useful for fever and pain in adults, but is not used in young children due to the risk of liver disease (Reye's Syndrome). A drug called Amantadine TM can be given to those with life threatening disease, although it has significant side effects. Some complications require antibiotics. People with chronic lung disease are often given antibiotics the moment flu is diagnosed to prevent the other infections.

Two new treatments for influenza are now available, Relenza and Tamiflu. However both of these medications only help if they are taken within 48 hours of developing symptoms. Neither medication has any effect on the common cold, and they are not recommended for use in children under 12 years of age. Neither of these newer medications has any major side effects.

How is influenza and its problems prevented?

Prevention is the best treatment. A healthy lifestyle, proper diet, not smoking and exercise will all help.

Vaccination is an effective way of avoiding the flu. Unlike other infectious diseases, the flu virus changes and different varieties occur each year. That means that vaccines need to be changed on a yearly basis. This ensures they are effective against the virus type most likely to affect the community in the coming season.

All high risk persons should be vaccinated with a new vaccine each year since yearly vaccination has been found to be effective in preventing severe symptoms. It can be lifesaving in many cases. 

Doctors, nurses and others caring for high risk people should be vaccinated. Medical nurses looking after patients with immunity problems should also be vaccinated.

Can you get influenza from the vaccine?

It is impossible to get influenza from the vaccine. Unfortunately the vaccine is given at a time when other flu-like illnesses circulate within the community and any symptoms you get at this time may be due to other infections caught around the time of vaccination.

The influenza vaccine contains strains of the vaccine that have been killed and split. What is actually given by injection is only the part of the virus that will protect you from the disease.

What about reactions to the vaccine?

Most people have little or no reaction to the vaccine injection. One in four might have a swollen red tender area where the vaccine was given. Occasionally slight fever and chills, or even worsening of chest symptoms may occur in those who already have chest disease. These rarely last longer than one or two days. Because the vaccine is produced in eggs, people who are allergic to eggs should not receive the vaccine unless it is absolutely necessary.

Can you get influenza more than once?

A person can have influenza more than once because there are 3 flu virus families (A B and C). Within each family are many strains against which your immunity (antibody levels) may be less effective or ineffective against an unfamiliar strain.

Every 10 years or so a very different strain appears which may cause a major world-wide epidemic. This occurs when a population does not have any antibodies effective against that new strain. One such influenza epidemic in 1918 left more than 20 million people dead.

Please Note: This information is intended by The Australian Lung Foundation to be used as a guide only and is not an authoritative statement. Please consult your family doctor or specialist respiratory physician if you have further questions relating to the information provided here.

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Content updated May 2004