General Practitioner, Dr Daniel Grossman sheds some light on what the flu is, and what we can expect this year.

Influenza (more commonly known as the flu) is an illness that many of us have experienced, but there is still often confusion about:

• what influenza (the flu) really is
• how dangerous it really is
• how it should be managed/ treated
• how it can be prevented/ avoided.

What is influenza (the flu)?

Influenza is an illness caused by a highly contagious virus, usually spread in droplets of fluid that are produced when an infected person sneezes or coughs.

The influenza viruses are divided into three main groups, called influenza A, B and C, depending on the different types of protein molecules that the virus caries.  Influenza A is further categorised according to its surface features known as hemagglutinin (H), and neuraminidase (N), which play a role in entering our cells and spreading the virus, respectively.

A person can be infected with an influenza virus when they breathe in tiny particles of fluid (from another person’s sneeze/ cough) that are suspended in the air, or after touching an infected person’s hand, or even a surface that has been touched by an infected person.  Once the virus gains entry into our cells lining the nose/ throat/ lungs, it can replicate, then infect other adjacent cells.

Symptoms of the flu typically develop around 18-72 hours after a person is infected with the virus.  These usually include an abrupt onset of fever/ chills, respiratory symptoms (e.g. cough, sore throat, runny nose), headache, body pains and general malaise.  After the quick onset, the fever tends to settle in 2-5 days, but the cough and sore throat may last longer, and tiredness/ weakness may even persist for weeks.  When the flu is on the milder side, it can be difficult to differentiate from the common cold, which is caused by different viruses. 

How dangerous is influenza (the flu)?

Outbreaks of influenza are recorded just about every year, with variable extent and severity.  Global flu pandemics have occurred most recently in 2009-10 (influenza A/H1/N1 or ‘swine flu’), 1968-69, 1957-58 and 1918-19.  Influenza type A tends to cause the worst outbreaks because the virus can change its surface structures frequently, so that our immune systems don’t ‘recognise’ the virus, and it retains its ability to replicate and spread. 

‘Swine flu’ refers to those types of influenza A viruses that infect pigs. They do not usually infect humans, but a variant emerged in 2009 which could infect humans as well as pigs, and this resulted in the H1N1 pandemic.  This particular flu spread widely from person to person, but eating properly cooked pork did/ does not pose a risk of influenza infection.

Influenza viruses can occur throughout the year in tropical regions, but tend to be restricted to the winter months in the temperate climates of the northern and southern hemispheres, unless a pandemic occurs.

Most healthy people who become infected with influenza make a full recovery, but certain people are more vulnerable to a more severe illness, complications, or even sometimes death.  We know that the following groups of people are usually at increased risk:

• anyone aged 65 years or older
• children under 5 years of age
• pregnant women
• Aboriginal and Torres Strait Islander people ≥ 6 months - 5 years, and ≥ 15 years
• people with chronic heart disease, lung disease, kidney disease, neurological conditions, Down syndrome, impaired immunity, diabetes, alcoholism, obesity or haemoglobinopathies
• residents of nursing homes and other long term care facilities
• homeless people
• people with severe asthma
• children on long term aspirin therapy
• people with other chronic illnesses that require regular medical follow up or hospitalisations.

Possible complications of influenza infection include:

• primary influenza viral pneumonia
• secondary bacterial pneumonia
• sinusitis
• otitis media (middle ear infection)
• Reye’s syndrome (liver and brain swelling in children)
• rhabdomyolysis (muscle breakdown and kidney damage)
• myocarditis/ pericarditis (heart inflammation)
• encephalitis (brain inflammation)
• Guillain-Barre syndrome (spreading paralysis)
• exacerbation of underlying heart, lung or other chronic disease states.

It has been estimated that over 3000 influenza deaths occur each year in Australians over 50 years of age, and over 13,500 Australians are hospitalised.

How should influenza (the flu) be managed/ treated?

Doctors will often make a flu diagnosis on the basis of the symptoms and examination findings, but tests are sometimes used to confirm the diagnosis (e.g. a swab from the nose/ throat).  We still don’t have a cure for influenza and most cases are managed symptomatically with measures such as rest and paracetamol. 

Specific antiviral therapy is available, but still a little controversial in terms of how effective it really is.  There is some evidence that a course of certain antiviral medications will reduce the duration of uncomplicated influenza by a day or so, if treatment is started within 2 days of onset of the illness.  Some flu viruses are exhibiting resistance to some of these drugs, and there can be side effects from the medications.  It is not clear how well these drugs work to reduce the risk of complications, but one of these drugs may reduce lower respiratory complications and hospitalisation rates.

How can influenza infection (the flu) be prevented/ avoided?

Because of the way influenza is transmitted (see above), it follows that frequent and thorough hand washing, careful use of disposable tissues and avoiding close contact with other people, will go some way to reducing the risk of passing on the virus when someone is infected.

Immunisation is the other key strategy we can use to avoid influenza infection.

Each year, the World Health Organisation (WHO) tries to predict the most likely strains of influenza that will be circulating in the approaching flu season.  The Australian Influenza Vaccine Committee decides on the composition of the vaccines for use in Australia.  These predictions and decisions inform which strains are covered by the immunisations manufactured by pharmaceutical companies, and there can be significant changes from year to year. 

Whilst the predictions are often accurate, one of the flu strains included in the northern hemisphere vaccine for 2014-15 winter did change just enough to make the vaccine ineffective against this strain, resulting in a relatively severe flu season there.  Changes have been implemented for our southern hemisphere vaccine this winter (2015), which we hope will improve the vaccine efficacy here in Australia. 

These changes have delayed the manufacture of the vaccines, however, and our vaccines are not going to be widely available until April this year, instead of the usual March release.

The flu vaccine contains fragments of inactivated flu virus, which cannot cause influenza, and side effects are not common.  Mild fever, malaise and muscle aches may occur in 1-10% of flu vaccine recipients; this tends to settle within a couple of days.  Rare cases of febrile convulsions have been reported in children under 5 years of age.  There can be a bit of soreness, redness or a lump at the injection site in a minority of people too.

It takes 10-14 days to achieve a full response to the vaccine, but some degree of protection may develop more quickly.  The efficacy of the flu vaccine depends on factors such as the age of the recipient and the strength of their immune system, as well as how well the vaccine ‘matches’ the circulating flu virus(es).  The vaccine is generally effective for about a year, with annual re-vaccination required to achieve ongoing protection.

It is recommended that people in the ‘at risk’ categories listed above undergo annual influenza immunisation, as well as people who may transmit influenza to the vulnerable:

• healthcare providers
• staff in nursing homes/ long-term care facilities/ early childhood education & care
• those providing care for the homeless
• household contacts of those in the high risk groups.

Furthermore, anyone providing essential community services can go some way to reducing disruption from influenza infections by getting vaccinated.  Employers should consider the potential benefits of immunising their workforce against influenza, for the same reason.  And travellers might avoid serious disruption to their trip if they are protected, too.

Even though the flu vaccine is manufactured using hens eggs, the residual quantity of egg material in the final product is so small that it can usually be given to people who have had allergic reactions to eggs previously.  The supervising doctor should be informed about egg allergy (and other allergies) prior to administration of the vaccine, so that the correct advice/ precautions can be discussed.

A free government supplied flu vaccination is available in 2015 for people in the above at-risk categories (excluding non-ATSI children < 5 years, alcoholism, obesity, Down Syndrome and homeless people - unless they fall into one of the other categories).

So, to protect yourself and others from influenza (the flu) in 2015:

• Talk to your doctor about vaccination if you think you may be at risk of complications or more severe influenza
• Consider vaccination to minimise risk of disruption at work, or when travelling
• Keep up with any recommended management  or medical follow up of any chronic medical conditions.

And if you do become unwell:

• Wash your hands frequently and thoroughly
• Use disposable tissues
• Try to avoid any non-essential contact with other people
• Ensure you get adequate rest and fluids
• Consider using paracetamol to help with fever, aches and pains
• Consult your doctor if you have any concerns about complications or symptoms that you are not able to manage.

Free fact sheet!

To help you provide your teams with all of the information they need regarding the 2015 flu, we've developed the below factsheet.  To download, simply click on the link at the bottom of this page.