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 it 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 and 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. Breathlessness can occur if more severe complications such as pneumonia develop.

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 is at risk?

We all are at risk for getting and spreading the flu. Health problems which make people more likely to develop the complications of influenza include:

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


The flu is caused by influenza viruses that infect the nose, throat, and lungs. These viruses spread through droplets in the air when people with flu cough, sneeze or talk. The virus can also be spread by touching a surface or object that has flu virus on it and then touching your own mouth, eyes or nose. You can spread the flu before you know you are sick, beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick.


Flu symptoms often appear suddenly. People at higher risk of complications, such as those with chronic lung disease, should seek prompt medical attention.

Symptoms of influenza can include:

  • Sore throat
  • Fever and chills
  • Headache, muscle aches and joint pain
  • Dry, chesty cough
  • Nasal congestion and runny nose
  • Fatigue
  • Sneezing
  • Nausea, vomiting or diarrhea
  • Most people recover from the flu within one or two weeks, but others, especially the elderly, may feel weak for a long time even after other symptoms go away.


Your doctor may diagnose a probable influenza infection based on your symptoms alone. They will listen to your chest using a stethoscope. If your doctor wants to be sure of the diagnosis they may take a sample of cells and mucus from your nose or throat using a sterile cotton swab. This sample will be sent to a pathology laboratory for testing.

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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).

Relenza and Tamiflu are two medicines available for the treatment of influenza, however, they only help if taken within 48 hours of developing symptoms. These medicines do not have any effect on the common cold and they are not recommended for use in children under 12 years of age. People with chronic lung disease may also be given antibiotics to prevent the onset of bacterial infections which may worsen influenza.



Prevention is the best treatment. A healthy lifestyle and diet, not smoking and exercise will all help. Vaccination is an effective way of lessening the chance of catching influenza. 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 staff and 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. As the vaccine is given at a time when other flu-like illnesses circulate within the community, 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 broken apart. 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 lung 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.