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

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 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?

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?

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 2 nd twin was more severe…

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

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

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?

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!

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 year olds?

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 …..