About influenza

Influenza (the flu) is a highly contagious viral infection that can cause severe illness and life-threatening complications, including pneumonia. The flu is spread by contact with fluids from coughs and sneezes.

It is estimated that flu contributes to over 3,000 deaths in Australia each year.

The 'swine flu' virus – also known as influenza A (H1N1) – emerged in 2009 and caused the first influenza pandemic in more than 40 years. However, it is now a regular human flu virus that continues to circulate seasonally worldwide. The current seasonal influenza vaccine has been designed to include protection against the swine flu virus.

Find out more about the flu.

Our guests

Victorian Deputy Chief Health Officer (Communicable Diseases) - Dr Brett Sutton

Photo of Deputy Chief Health Officer Dr Brett Sutton

Dr Brett Sutton has extensive experience and clinical expertise in public health and communicable diseases, gained through emergency medicine and field-based international work, including in Afghanistan and Timor-Leste. He represents Victoria on a number of key national bodies including the Communicable Disease Network Australia. He is also Chief Human Biosecurity Officer for Victoria. Dr Sutton has a keen interest in tropical medicine and the incorporation of palliative care practice into humanitarian responses.

Director, WHO Collaborating Centre for Reference and Research on Influenza (Doherty Institute) - Professor Kanta Subbarao

Photo of Professor Kanta Subbarao

Professor Kanta Subbarao is the Director of the World Health Organization Collaborating Centre for Reference and Research on Influenza at the Peter Doherty Institute for Infection and Immunity.

Kanta is a virologist and a physician with specialty training in pediatrics and pediatric infectious diseases.

Her research is focused on newly emerging viral diseases of global importance, including pandemic influenza, severe acute respiratory syndrome (SARS) and Middle East Respiratory Syndrome (MERS), and includes study of virus biology and pathogenesis, immune responses to infection and vaccination, development and preclinical and clinical evaluation of vaccines.

  • Transcript

    Health information and awareness for all walks of life.

    The Better Health Cast brought to you by the Better Health Channel at betterhealth.vic.gov.au

    Hayden: Hello, and welcome to the Better Health Cast. I’m Hayden Nicholls. You may have heard or seen this advert in the past couple of months:

    Voiceover: The pain of the heat of that fever.

    The flu flattened me.

    I was really worried that I was going to give it to my kids.

    Four weeks on the couch.

    I couldn’t go to work, I couldn’t do nothing.

    I couldn’t eat or drink.

    I have an immunity issue so I can’t be near the flu.

    The flu triggered my asthma.

    Very sick.

    Just ‘gurh’.

    You really worry about your baby.

    It can be very deadly.

    I had a big trip to the hospital.

    I just remember thinking, ‘this is the flu’.

    Hayden: Today we’re talking about the flu. Influenza is a viral disease that causes widespread illness every year and can affect people of all ages and levels of health.

    In 2017 Australia saw the highest level of influenza infection since the 2009 pandemic flu season with more than 233,000 confirmed cases of influenza, compared to the 2016 season that saw over 87,000. What exactly is influenza? Why do we need to get vaccinated against it every year? How do we stop the spread of it? What is being done about it?

    To answer these questions and more I’m speaking with two experts. We’ll hear from Victoria’s Deputy Chief Health Officer of Communicable Disease, then from a world leading expert who runs the World Health Organisation’s Collaborating Centre on Influenza from the Doherty Institute, to get the science behind the evolving flus that we see each year.

    First up is Dr Brett Sutton, Victoria’s Deputy Chief Health Officer of Communicable Disease who – well I’ll just let him introduce what he does.

    Brett: I’m the Deputy Chief Health Officer. I’m one of the two Deputy Chief Health Officers and I am the Deputy who looks after all things infectious, Deputy Chief Health Officer for Communicable Diseases and that covers our Immunisation Team, the teams that track all of our notifiable diseases and respond to them, as well as the Partner Notification Unit and some oversight of our TB activities as well.

    Hayden: Brilliant, just the man we need to talk to then. What is influenza?

    Brett: Influenza is a virus. It’s a virus that is always circulating but has a real winter season to it. In the Southern Hemisphere that essentially means that it happens between May and September/October with a peak around July/August and it’s really one of the most severe communicable diseases that I have to deal with because it affects so many people and it can really be quite deadly.

    Hayden: How does the flu affect us?

    Brett: I think it’s really important that people understand that it’s not like your average cold. I think the sniffles that we can all get with a runny nose and a sore throat or a cough is not the same as the flu. The flu affects us much more severely, it knocks people for six. Some people can get it more mildly but a lot of people will be absolutely floored by influenza. It means taking a week or two or more off work, you can not lift your head off the pillow, not get off the sofa for a week, you can have severe headache, high fevers and chills, muscle aches and pains, joint aches and pains, and obviously it can also land people in emergency departments and can kill those who are most vulnerable. 

    Coughing and sneezing will be the main way that it transmits, but it’s also on surfaces including our hands so we can transmit it to others by the surfaces that we touch, the telephones, the keyboards, the handrails, public transport, and the frequently touched surfaces that we have means that it’s very easy for others to touch that, and you wouldn’t realise it but we touch our faces several times a minute without even knowing about it and that makes it easy for flu to spread to others.

    Hayden: How do we protect ourselves against the flu? What are the best strategies?

    Brett: The really key thing is the vaccine. There’s been lots of talk about vaccine, does it do a great job, does it do a good job, does it make it worse? The bottom line is you can have vaccines that are somewhat more effective some seasons, somewhat less effective other seasons, but it’s always going to be better than not being immunised. Getting immunised is the key thing to protect you from the flu, but there are other things that you can do, obviously staying away from work, staying away from crowded places, and staying away from vulnerable people when you’re unwell are really key things to help protect others from the flu. Coughing and sneezing into your elbow rather than your hands, so wrapping your arm around your nose and sneezing into your elbow is going to be better because if it gets on your hands you’ll spread it to others, but if you’re going to use a tissue make sure that you throw it straight away into the bin and wash your hands frequently with soap and water.

    Hayden: We had a very long flu season in 2017, what were the circumstances around that?

    Brett: It was long and it was big and it was pretty severe in the sense of the number of people who needed to see their GPs, go to emergency departments, and who were hospitalised and ultimately the numbers who died as well. It was just a really big season. One of the main reasons for that is that one of the strains of flu that was really predominantly circulating, called H3N2, affected the elderly much more and so our elderly population who are particularly vulnerable were hit very hard with it. So there were a number of outbreaks in aged care settings, there were a number of people who needed intensive care, who needed hospital and there were also significant numbers of kids who became unwell who also sometimes needed intensive care, and there were a few children tragically who died as well in 2017.

    Hayden: You just spoke of children and the elderly there as being some of the vulnerable groups, are there any others?

    Brett: Anyone over 65 and Aboriginal and Torres Strait Islander people over 50 years of age are considered vulnerable, but anyone really with a chronic medical condition, so if you’ve got emphysema or some other lung disease or heart disease, diabetes, if you’re a smoker, if your immune system is poor, then you should be considered vulnerable, and children under five. All of those groups including pregnant women as well are considered vulnerable.

    Hayden: We’ve had a lot of other communicable diseases in the news lately, stuff like Hepatitis A, measles, meningococcal disease, how does the flu compare to those other diseases on the scale of strength and effect on the community?

    Brett: I guess there are some really awful diseases like meningococcal disease that are more severe, but compared to influenza they’re very rare and if you look overall on the effects of flu in the population compared to all of our other communicable diseases it’s really the most significant illness. It will hospitalise more people and unfortunately it will kill more people than all of our infectious diseases put together, and that’s why we just need to do everything in our power really to protect ourselves from it.

    Hayden: What are some common misconceptions that are out there in the community about flu that you’d like to address?

    Brett: I think a lot of people talk about getting the vaccine and then feeling unwell afterwards and said, “I just got the flu”. Some people might get the flu after the vaccine but it’s not from the vaccine. The vaccine is a dead vaccine so you can’t get influenza infection, the vaccine is dead. People might get some side effects from the vaccine, the local soreness, inflammation and swelling where the injection has been given in their arm, they might even get a low grade fever or some mild aches and pains. That’s their immune response to the vaccine, that’s not getting the flu, but you’re also not completely immune until you’ve had the vaccine for two weeks. You could be unlucky enough to get influenza in that two week period before you are protected. Of course lots of people get some kind of viral illness during the winter season, including just after they’ve gotten the flu vaccine, but with literally hundreds of viruses that can give you cough and cold symptoms it’s often not the flu, in fact most of the time it’s not the flu. Unless you’ve had a swab that comes back with confirmed influenza then you can’t say it’s the flu. 

    Some other ones is that you need antibiotics to treat the flu. The flu is a virus, viruses don’t respond to antibiotics. If you happen to get a bacterial infection on top of the flu, that’s quite uncommon, then you might need antibiotics but for the great majority of people it’s a case of rest, fluids, staying at home and taking the time to recover. Vulnerable people who might need antiviral medication for flu if they’re particularly vulnerable to severe infection, but their GP will talk to them about getting antivirals, but most people don’t need antibiotics that’s for sure.

    Hayden: We’ve just heard about what the flu is and how it’s transmitted. Let’s go further. How and why does the virus change every year? How does that affect the protection that you get from your flu vaccine? To find out more we spoke to Professor Kanta Subbarao the Director of the World Health Organisation’s Collaborating Centre for Reference and Research on Influenza. As you would expect from a title like that, Professor Subbarao is one of the world’s leading researchers on influenza at the frontline of the battle to get ahead of the flu each season with the latest vaccines. She is based at the Peter Doherty Institute for Infection and Immunity in Melbourne.

    Kanta: The World Health Organisation recognised about 65 to 70 years ago the need for a global network of influenza surveillance. So they set up laboratories around the world in different countries that monitor influenza throughout the year. They report to one of five what are called WHO Collaborating Centres; one is in the US, one in the UK, one in Japan, one in China and one in Australia.

    Hayden: What is the flu? How would you describe the flu?

    Kanta: The term the ‘flu’ that people use refers to the illness that is technically called ‘influenza’. The illness is called ‘influenza’ or the ‘flu’, the virus that causes it is an influenza virus. There are several types of influenza viruses, A, B, C, and D. A and B cause epidemic or seasonal influenza outbreaks.

    Hayden: You have an interest in paediatrics, what effect does the flu have on babies and young children?

    Kanta: Very young children under the age of one and particularly under the age of six months of age can present with just a high fever. They may not have any respiratory signs and in fact the two extremes of age are where we see the most hospitalisations and mortality from influenza, so the very young and the very old are at highest risk for complications of influenza. In addition, young children can shed the virus for longer and they’re the ones who actually spread the virus in communities, so they bring it home and introduce the virus into households. In fact there are several countries where the emphasis is on vaccinating children in order to try to break the epidemic spread of the virus, and this is being done now in the United Kingdom where there is a vaccination program designed immunising school aged children and they’re seeing benefits in other age groups as well. We currently do not have any vaccines available for use in children under six months of age and yet they are at high risk for severe illness, so it is strongly recommended that pregnant women get vaccinated in order to protect their young infants as well.

    Hayden: Let’s break it back down to basics again. What is a vaccine?

    KantaA vaccine is a preparation that is designed to induce immunity against a pathogen.

    Hayden: What happens to the body after it has a vaccination?

    Kanta: Vaccines are designed to elicit the type of immune response that the pathogen would under normal circumstances, so the idea is that we first have to identify which part of the immune response to a pathogen is protected. We have to identify when somebody has been infected with the pathogen, a virus or a bacteria or a parasite, there is a host response to the infection and we have to sort out which part of that immune response protects them from reinfection. Once we know what that element is then we can design a vaccine to elicit that element of the immune response without producing the disease that would happen with the natural infection.

    Hayden: Some people think it’s better to go through the flu without a vaccine as they will build up more antibodies.

    Kanta: As best as we understand, natural infection will give you a more complete immunity to the virus that you were infected with, because the vaccine is enriched for only two of the proteins of the virus and you don’t make a cell mediated immune response to all the components of the virus. So there is no doubt that a natural infection produces a more complete immune response than the vaccine does, but the principle of the influenza vaccine is to introduce antibodies to the hemagglutinin which is the major antigen to which the protective immune response is directed. So the argument against just going through and having a natural influenza infection rather than being vaccinated is because we cannot predict who will get a severe illness when they become infected with influenza. We know that there are certain people that are at high risk of severe complications but anybody in any age group could get quite sick with influenza, and the second problem is that they could also transmit the virus to somebody who is at high risk for complications. So that is the argument against opting to have a natural infection rather than vaccination.

    Hayden: What’s the process that’s followed for updating the flu vaccine every year?

    Kanta:The influenza viruses are able to change in nature, they evolve continuously in nature, and when people are infected with an influenza virus they don’t get lifelong protection, so unlike measles where if you have measles once you’re protected for life or you get the measles vaccine once and you’re protected for life, influenza viruses do not protect for life because they are able to change. So that change that occurs in influenza viruses is designed to evade the body’s immune response, and when they evade the immune response they change their characteristics sufficiently to be able to reinfect the same person a few years later in serial outbreaks.

    The influenza vaccine has to be updated in order to keep up with the natural change that’s occurring as influenza viruses evolve, so we continuously monitor influenza viruses around the world. We monitor how the viruses are evolving in nature and whether they have evolved away from last year’s vaccine. If last year’s vaccine is unlikely to protect against the new variants of influenza that are circulating we would update the vaccine. 

    There are four components to the influenza vaccine that represent the four influenza viruses that commonly cause epidemics. There are two influenza A viruses called A-H1N1 and A-H3N2 and two lineages of influenza B viruses. Unfortunately we cannot predict which of these four will predominate in any given season. There are seasons when a single virus of these predominates and there are other seasons when two or more co‑circulate, but because we cannot predict which one will circulate or dominate in the coming season the influenza vaccine contains components that cover all four possibilities.

    Hayden: How do the different strains of the flu arise?

    Kanta: When we think about how different strains of flu arise, I mean you could take the big picture and say ‘How do completely novel influenza viruses arise?’ The natural reservoir of influenza viruses in nature is in water fowl and shoal birds. There are many different subtypes of influenza A viruses. So far there are 18 HA subtypes that have been described and 11 neuraminidase subtypes that have been described, and a subset of those infect pigs and in the last 100 years we’ve had four pandemics of influenza where novel influenza viruses have been introduced into humans. In each of these instances they have been animal influenza viruses that have been introduced either from birds or from pigs. In some cases that introduction is the whole virus comes across from an animal reservoir into people, and that’s what happened in 2009, but in the previous two pandemics which were in 1957 and 1968 there was what we refer to as a re‑assortment event where two influenza viruses infect the same host and the viruses replicate. The daughter viruses that emerge have the right number of gene segments but they could be derived from either parent virus. So when a particular gene constellation comes together that is able to infect people and spread from person to person we have the introduction of a novel influenza virus that can cause a pandemic if the human population is not immune to it. That’s where novel influenza viruses come from. 

    Where do seasonal influenza viruses come from each year? We believe they are maintained in humans and the genome of influenza viruses contains RNA and when RNA is copied it cannot correct for mistakes, so there is a natural error rate in RNA viruses that is quite high. In addition, the antibody pressure from the host drives the virus to want to change. This is what is referred to as antigenic drift, again it’s happening all the time, and that’s why we have to update vaccines.

    Hayden: Is there any thought as to why it’s so prevalent in birds especially?

    Kanta: The main reason is that the viruses have reached an ecological stasis in birds so they don’t cause disease in birds so they’re maintained because they don’t induce an immune response, they don’t induce an illness and they’re just carried along and replicate to very high titre. It’s a very successful ecological relationship between an influenza A virus and birds. Influenza B viruses in distinction from influenza A viruses do not have an animal reservoir. The only source of influenza B viruses are humans and that’s why we don’t have pandemics of influenza B viruses. We only have pandemics of influenza A viruses.

    Hayden: If we are the main carriers of influenza B does that mean that we might have a high chance of being able to combat it?

    Kanta: Yeah, that’s a great question. We usually answer it more the other way around which is saying that influenza A viruses are not eradicable because of the animal reservoir, so technically because influenza B viruses do not have a non-human reservoir in theory one should be able to eradicate them, but because of the seasonality of influenza and the fact that viruses circulate in the Northern or Southern Hemisphere or the temperate part of the world at any given time, the idea of completely eradicating this virus is quite challenging.

    Hayden: Thank you so much for taking the time to speak to us.

    Kanta: Thank you very much.

    Hayden: Now we know more about the mechanics of how flu treatments are created, but what are the best steps to take if you want to avoid the flu? Here is Brett Sutton again with his advice.

    Brett: Certainly get vaccinated number one. If you’re unwell stay home. Wash your hands and cough into your elbow. If you’re sick keep up your fluids and rest and avoid the emergency department if you can.

    Hayden: There you have it, solid advice and a fascinating insight from two experts in influenza health communications and research.

    A big thank you to Brett Sutton and Kanta Subbarao for taking the time to speak with us. 

    If you’d like to learn more about the work of the Doherty Institute, a good place to start is their website at doherty.edu.au

    For more information on influenza and other topics head to the Better Health Channel at betterhealth.vic.gov.au

    Be sure to follow us via the Better Health Channel Facebook page to keep up to date on health info and subscribe to the podcast for more discussion on a range of health topics.

    The Better Health Cast was produced by Steve Marty, Jo Wellington, Meghan Cue and Hayden Nicholls for the Better Health Channel. Thanks for listening.

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Last updated: September 2018

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