The Truth About Influenza: Mild and Severe Disease

2. Influenza Professor Robert Booy NCIRS, University of Sydney February 25th , 2016

5. The double truth about influenza:mild and severe disease • Most cases cannot be distinguished from a common cold • About 25% have the classic flu presentation.. • Influenza is, by far and away, the most common cause of vaccine preventable disease AND DEATH in Australia • The annual number of deaths is 2000-3000 • But the number of those deaths that are proven by laboratory diagnosis is 5% or fewer – can you think of a personal example? • Almost all the deaths are in older people but there are about 5-15 deaths in children annually – more than any other VPD – how many die each year from other causes? • Children are over-represented in terms of GP visits & hospitalisations – which age groups of children are especially at risk? • From what age do we vaccinate? Do we adjust the dose?

6. A recent example: intelligent, informed and motivated parents • Identical twin girls aged 6 years returning from family holiday in the UK during January; PMH of severe flu • One developed cold symptoms en route in Singapore – within two days the other twin and the father both developed high fever, lethargy, sore throat and cough • GP did a diagnostic test – what ? • What treatment was given ? • Were they immunised? • How effective is immunisation? Flu A? B? age-based? • Is there cross-immunity between A strains or B strains?

7. Past medical history • Both girls actually had proven & severe influenza A, two winters ago in Australia • One was so severe she developed life-threatening pneumonia: required intensive care admission and respiratory ventilation • Her parents worried she might die • She thankfully improved and was discharged after two weeks in hospital – another 18 months before her general health & development matched that of her identical twin – I followed them in my OPD • BOTH TIMES, the 2nd twin was more severe…

8. Two brothers with influenza • Aged 1 and 4 – the older one got ill first • Then the infant, who developed encephalitis • They were of Chinese/Vietnamese background – why relevant? • Flu causes a number of life-threatening infectious complications – brain, lung, heart, sepsis, other? • Such cases are seldom predictable – both these boys & the twin girls had no prior or chronic illness - underlines the importance of PREVENTION

9. A 73 year old man with emphysema • Retired early (62) after long smoking history • Frequent acute respiratory infections, esp’ly in winter • Mid-July developed fever, cough, SOB, runny nose and then pneumonia – managed by GP • Wrote a letter to his son • 3 days later, had a myocardial infarction and died • No tests, no treatment, no formal diagnosis • No immunisation for him or his wife • Carers can become killers: households, aged care facilities

10. Herd Immunity: How important is it for the control of influenza? The importance of implementing vaccination programs • Who are the at-risk groups for whom the national immunisation program provides free protection? • So many of those for whom we recommend influenza immunisation may not respond as well as a healthy person – What can be achieved next month while waiting for Quadrivalent flu vaccine? • The very young and the very old are especially at risk and yet these are the very populations in which we fail to vaccinate/cannot vaccinate/won’t vaccinate … why?

12. Herd Immunity • A safety net to protect those who missed out on direct immunisation, or whose immune systems weren't able to mount sufficient defence against the disease-causing virus • Immunisations are for the whole family and protect the whole family, they are for institutions where people live, they are for workplaces, especially hospitals • You couldn’t go on a construction site without a hard-hat or drive a car without a seat belt • Indeed influenza vaccination is recommended for ANYONE who wishes to protect themselves against this disease!

13. Herd immunity • The public can be blasé about vaccine preventable diseases, because the very success of vaccination programs means they rarely encounter them anymore – eg polio 50 yrs ago; what recent outbreaks? • The importance of determining cost effectiveness and the role of the PBAC – • recent recommendation for flu vaccine in indigenous children aged < 5 years • What about 50-64 year olds?

14. Diagnosing influenza • How easy is it to diagnose influenza? • How does it compare to the common cold? • Is there a test that GPs can do in their surgery or that can be sent to a laboratory? • How often are cases of influenza formally diagnosed ? And what percentage of positive cases get specific antiviral treatment – in primary care? In hospitals? • What is the impact of early diagnosis and treatment on disease? • Disease prevention is the key …..