Influenza, commonly known as the flu, is a highly infectious viral illness caused by influenza A or B viruses. It affects the nose and throat and may also affect the lungs.
In Australia, seasonal flu of varying severity occurs every year, usually between May and September.
Influenza is a notifiable condition1
How influenza is spread
The flu virus is spread when an infected person talks, coughs or sneezes small droplets that contain the virus into the air where they may be breathed in by people nearby. Infection may also be spread by contact with hands, tissues and other infected articles.
Signs and symptoms
rapid onset of fever
nausea, vomiting and diarrhoea in children.
Most people recover within a week, although the cough and fatigue may last longer. Flu is much more serious than the common cold. It can lead to pneumonia (lung infection or inflammation) and other complications, and even death, particularly in:
people aged 65 years and over
people with chronic conditions like heart disease, diabetes and lung disease.
Influenza and pregnancy
Pregnant women are more likely to have severe complications from the flu, especially in the second and third trimesters. While the flu virus does not cross the placenta and infect the baby while in the uterus, the high fever and any chest complications caused by flu can be potentially harmful to the baby. Because of these risks, a doctor may recommend antiviral medication for pregnant women with the flu.
There is no evidence that the antiviral medications used in Australia to treat flu are associated with adverse effects in pregnancy. Similarly, women may continue to breastfeed while taking antiviral medication. The best protection for the mother and baby is for the pregnant mother to have the flu vaccine, which is safe and funded at any stage of pregnancy.
Not all people with symptoms need to be tested for flu. The diagnosis may be suspected on clinical symptoms and examination (especially during the flu season) and may be confirmed by laboratory testing of mucus from the back of the nose or throat.
(time between becoming infected and developing symptoms)
Incubation is 1 - 4 days (average of 2 days).
(time during which an infected person can infect others)
Usually from 1 day before onset of symptoms until 7 days after the onset of symptoms. After 5 days the level of infectiousness is probably very low, however some people, especially children and people with weakened immune systems, might be able to infect others for a longer time.
Most people recover with rest, drinking plenty of fluids and use of paracetamol for the relief of pain and fever. Aspirin should not be given to children under 12 years of age unless specifically recommended by a doctor.
People with moderate or severe illness, pregnant women, Aboriginal and Torres Strait Islander people and those with chronic medical conditions may benefit from specific antiviral medication. This can reduce duration of symptoms by about 1 day and prevent some of the more serious complications of flu, but is only effective if commenced within 48 hours of illness onset.
Antiviral therapy may sometimes be used to prevent infection in close contacts of people with flu, such as vulnerable household contacts. A contact is any person who has been close enough to an infected person to be at risk of infection themselves.
When to seek medical advice
Seek medical advice if:
shortness of breath or difficulty breathing
symptoms are getting worse
you are concerned about the symptoms
children are unable to keep fluids down because of vomiting
children show signs of dehydration (dizzy on standing, passing less urine than usual).
Flu vaccines reduce the risk of getting severe influenza. Annual flu vaccination is strongly recommended for anyone 6 months of age and older and should be actively promoted for people at increased risk of complications.
Cover a cough or sneeze with a tissue or your arm, not with your hand. Drop used tissues immediately into a rubbish bin, then wash your hands.
Wash hands as soon as possible after sneezing or coughing and after contact with nose and throat discharges or articles soiled by these. Use soap and water or an alcohol based hand rub.
Use of the information and data contained within this site or these pages is at your sole risk.
If you rely on the information on this site you are responsible for ensuring by independent verification its accuracy, currency or completeness.
This site includes links to other websites operated by community, business and government.
These linked websites will have their own terms and conditions of use and you should familiarise yourself with these.
All linked websites are linked 'as is' and the Government of South Australia:
does not sponsor, endorse or necessarily approve of any material on websites linked from or to this Site;
does not make any warranties or representations regarding the quality, accuracy, merchantability or fitness for purpose of any material on websites linked from or to this Site;
does not make any warranties or representations that material on other websites to which this site is linked does not infringe the intellectual property rights of any person anywhere in the world; and
does not authorise the infringement of any intellectual property rights contained in material in other websites by linking this site to those other websites.
If you use automatic language translation services in connection with this site you do so at your own risk.
The information and data on this site is subject to change without notice. The Government of South Australia may revise this disclaimer at any time by updating this posting.
The Government of South Australia, its agents, instrumentalities, officers and employees:
make no representations, express or implied, as to the accuracy of the information and data contained on this site
make no representations, express or implied, as to the accuracy or usefulness of any translation of the information on this site or any linked website into another language
make no representations as to the availability of the site and the availability of websites linked from or to the site
accept no liability however arising for any loss resulting from the use of the site and any information and data or reliance placed on it (including translated information and data)
make no representations, either expressed or implied, as to the suitability of the said information and data for any particular purpose
accepts no liability for any interference with or damage to a user's computer, software or data occurring in connection with or relating to this Site or its use or any website linked to this site
do not represent or warrant that applications or payments initiated through this site will in fact be received or made to the intended recipient. Users are advised to confirm the application or payment by other means.