The flu season is upon us - so be prepared!

If you're feeling sick and think you have the flu, then go and see your doctor and stay away from your dentist. If you see your doctor within a day of getting the symptoms of influenza, then they can help.

But even if you're resolute about soldiering on through your bout of influenza, stay away from other people as much as possible as it can be a killer.

The more contact you have with other people, the more likely you are to spread the virus around. And some people will not cope as well as others.

Going to the dentist when you have the flu is a recipe for disaster!

The research shows that we are not taking proper precautions when we do get the flu.

The 2017 Australian flu season was the most widespread since the 2009 pandemic with more than 233,400 confirmed cases being recorded nationally. This is more than two and a half times the number of laboratory confirmed cases in 2016. A total of 745 patients died in 2017 compared with the 5-year average of 176 deaths.

Those most at risk of catching the infection were the elderly and young children. The peak of activity was in the colder months (March to October) with high activity persisting for a number of weeks and then slowly decreasing as spring approached. Victoria, New South Wales and Queensland reported the highest number of cases with Western Australia being hardly affected at all. In Tasmania, as of 12 September, 2,237 confirmed cases were reported with 21 deaths, six of which occurred in a nursing home of 37 elderly residents near Devonport, despite 95% of the inmates being vaccinated against influenza. Whilst the deaths of those aged 80 years or more or young children aged 5-9 years might cause some anxiety amongst dwellers in large cities, such deaths as in this small country town in north west Tasmania or the 7 similar nursing home deaths in Wangaratta (Victoria) can sometimes cause severe emotional problems in the local communities.

Whilst influenza A (H3N2) was the dominant circulating influenza virus through the season, influenza B (H1N1) also caused infections. Reports from laboratories as to the number of flu infections occurring in the population under estimate the prevalence of infection as many individuals are not so sick that they seek medical advice or are unwilling to go to doctors to be tested.

Each year, a new seasonal flu vaccine is developed to protect against the three or four influenza viruses research indicates most like to spread and cause illness during the upcoming flu season. More than 100 national influenza centres in 100 countries receive and test thousands of influenza samples and send results to the World Health Organisation (WHO), which then, twice a year, sends information to interested parties and five collaborating influenza research centres, one of which is based in Melbourne.

The US CDC plays a major role in testing and identifying new strains of virus through their global surveillance activities and sends this information to research centres, which determine which viruses will be included in the vaccine for the upcoming flu season.

In the Southern Hemisphere, including Australia, this decision is made each year in September and once notified, manufacturers begin the process of making the new vaccine. Vaccine viruses must be isolated and grown in chicken eggs by injecting seed virus into numbers of fertilized hen's eggs and then removing the viral containing fluid which is then inactivated and tested prior to mass production. This means it could take 6 months or more before sufficient vaccine is available to vaccinate a country's population. In addition, the H3N2 virus is slow to grow in eggs, making it difficult to produce enough vaccine and in some years, certain flu viruses do not appear and spread until later in the flu season and therefore are not included in the new vaccine.

Today's flu vaccines are not as effective as those for measles or human papilloma virus (90 to 97% effective) and it is common for only 60% of those vaccinated against flu to develop a protective immune response. In one study of the 2017 flu season, only 27% of Australians were vaccinated including just 6% of children. Of those vaccinated, 33% were effectively protected with less than 20% protected against H3N2 and 37% against influenza B.

Many explanations have been given for this low level of protection. These include a strain-vaccine mismatch due to alterations in the viral hemagglutinin changing antigenicity during the prolonged period of growth in eggs, mutations occurring in the virus during storage prior to use, early childhood imprinting, a lifetime of repeated vaccinations and infection and the lessened immune response in the elderly. However, despite years of influenza research, science does not have a complete understanding of how these factors influence vaccine production.

Nevertheless, the CDC, public health officials and most infectious disease physicians strongly recommend the use of flu vaccines. The vaccine does not cause the flu and partial protection is better than none. In addition, some recent research suggests that the flu vaccine prevents flu related hospitalisation, pneumonia and lower respiratory tract infection.

When it became known that the current vaccine in Australia was only partially effective, some of the lay press began implying that if Australia had purchased a high dose American vaccine called Fluzone, the flu epidemic would not have happened. Fluzone, which contains four times more antibody inducing hemagglutinin than normal vaccines, is licensed in USA and Canada for those aged 65 years or more but not for other age groups. However, Fluzone was not approved for use in Australia in 2017 but the manufacturer hopes to obtain such approval from the Therapeutic Goods Administration in 2018.

What lies ahead in 2018 in Australia and other countries?

The Australian Technical Advisory Group on Immunisation has already collated all the information regarding the types of influenza virus causing infections around the world and made recommendations as to the viral make up of the 2018 vaccine. Normally, the vaccines contain 3 recommended strains of virus, 2 current influenza subtypes and influenza B.

The Australian Immunisation Handbook 10th Edition recommends that children over the age of 6 months and individuals aged over 65 years should be vaccinated against influenza as should Aboriginal and Torres Strait Islanders aged between 6 months and 5 years and those over 15 years of age.

People of all ages with chronic diseases such as cardiac disease, chronic respiratory diseases, asthma, emphysema, impaired immunity, those who are pregnant or reside in nursing homes or long term care facilities and all health care workers should be vaccinated against influenza.

WHO has reported that flu infection levels are rising in Europe in 2018 with both H3N2 and H1N1 viruses involved. In Britain, health authorities are preparing for widespread infections due to the H3N2 virus for the strain, dubbed by the press as "Killer Aussie Flu", has already reached both Scotland and Ireland .The National Health Service is urging the public to be vaccinated against the flu but admits that the vaccine currently available is formulated the same as that which provided limited protection in Australia.

In the United States, flu activity rose sharply in late December 2017 with many states reporting widespread infection with 89% being due to H3N2 viruses and 11% due to H1N1. Similarly in Canada, flu outbreaks requiring hospitalisation involving H3N2 began early in winter and are expected to peak in January/February 2018. A significant problem for both countries Is that the H3N2 component of the available vaccine is the same as that which was only partially effective in Australia.

By Dr Vincent Amerena