Although the flu season has already started, health experts are reminding the public that it is not too late to be protected this winter.
NSW is already feeling the effects of an early start to the flu season.
The latest weekly Influenza Surveillance Report shows 6234 flu cases for the week ending July 7, up from 5590 notifications the previous week and four additional deaths, bringing the annual total to 70 confirmed deaths.
Influenza vaccination reduces the number of patients that need medical care, both at GPs and hospitals, making space available for those who urgently need care.
It is estimated that, each year, influenza causes an average of 13,500 hospitalisations and more than 3000 deaths among Australians aged older than 50 years.
Clinical microbiologist and virologist, Professor David Smith, says influenza imposes a huge health, social and economic burden on communities each year.
"Those who choose not to be vaccinated magnify that burden," he said.
"There is the obvious personal health risk of being unvaccinated, especially to those who are vulnerable to severe influenza, but also the lost work time and income, caring for sick children, and also exposing others to influenza. The vaccination is safe and there are very few scientifically valid reasons for people not to get vaccinated."
He says the flu shot is particularly important in those who are at high risk of severe influenza, including pregnant women, anyone aged 65 years or older (even if they are healthy), Aboriginal and Torres Strait Islander populations aged 15 years or older children under five years of age, and people with any chronic illnesses including heart disease, respiratory disease, diabetes or neurological diseases, those who are very obese, and people with a poor immune system due to a disease or treatments that depresses the immune response.
"Vaccination of pregnant women is particularly important not just to protect the mother and baby while it is still in the uterus, but also to protect the baby in the first few months of life," Professor Smith said.
"They rely on antibodies that have crossed the placenta from the mother to protect them.
"Of course, good personal hygiene practices are always recommended to help reduce your risk of getting or spreading influenza and other respiratory viruses, however the single best preventive measure against influenza is to get vaccinated one to two months before the beginning of the season."
Influenza virus is a respiratory virus, meaning it mainly causes infections involving the lungs, airways, nose and throat. Infections are usually mild, however high fevers, aches and pains, cough, and a sore throat are common.
Sometimes, and especially in pregnant women, young children, older people and people with chronic illness, the virus causes pneumonia. Rarely, it can also spread to involve the heart, brain or muscles. Influenza infection also increases the likelihood of bacterial infections, ranging from middle ear and sinus infections, right through to fatal bacterial pneumonia.
There are two main types of influenza viruses that cause infections each year, influenza A and influenza B, both of which are found worldwide. Influenza A is the most serious of these and is found in both humans and animals.
The influenza A/H1N1, influenza A/H3N2 and influenza B viruses that are currently circulating in humans continually change their surface proteins, so they are not affected by the protection built up from previous infections or vaccinations. This is why people can get multiple infections in their lifetime, the reason why the vaccine has to be changed each year.
"Influenza is notoriously difficult to predict, and this year's season started earlier than usual with a high circulation of two viruses which are causing problems; an influenza A/H3N2 strain and an influenza B strain," Professor Smith said.
"However, we won't really know how bad the season will be until later when we know how big the peak of the season is and how long it lasts. We can't be sure whether a season is going to be mild, moderate or severe, so if people wait until we know how bad it is going to be, then their vaccination will be too late to give them protection throughout the season."
Basic hygiene is particularly important for people visiting elderly relatives at aged-care facilities. In the year to date there have been 126 confirmed influenza outbreaks in aged-care facilities, 14 of which were reported recently.
Although there has been strong demand, there are sufficient supplies of free government-funded vaccines available for eligible people.