Revealed: How people born before 1968 are more at risk of getting nasty 'Aussie flu'
What are the odds of you getting the nasty 'Aussie flu', the A(H3N2) strain, that has swept the country and looks set to linger for another six weeks?
One risk factor may be whether you were born before 1968. An adult's chances of falling ill from a strain of flu are at least partly determined by the first ever type of virus they encountered as a child.
"Our best immune response will be to those viral infections we acquired first," said Dr Cillian de Gascun, head of the National Virus Reference Laboratory in UCD.
"People born before 1968 would have been exposed to influenza A (H1N1) or A (H2N2) in their childhood.
"As such, in simple terms their immunological memory response is probably suboptimal for A (H3N2).
"This might explain why the disease affects this age group disproportionately."
The latest figures for those hospitalised with flu so far this winter show a rate of 8.4 per 100,000 among the 55-64 year age group compared to 6.5 per 100,000 in the 35-44 year olds.
Older people's reduced defences also make them more vulnerable and the rate among the hospitalised over-65s is 42.3 cases of flu per 100,000.
Flu has arrived with a blast in 2018.
Around 20,000 people in Ireland fell victim to flu-like illnesses in the past week - mostly due to a B strain of the virus .
The 'Aussie flu' is also raging, as is a swine flu to a lesser degree.
This year was forecast as 'The Year of the Flu.' But in Ireland at least it looks like it will not live up to the billing as the "worst outbreak in living memory" - although the numbers so far laid low with flu-like illness this winter are the highest in around seven years.
People with underlying illnesses continue to be at highest risk, but it has also struck healthy people including young children.
The fact it comes against a background of the post-Christmas meltdown and trolley crisis in hospitals gives this flu season a particularly grim profile.
However, there is no evidence so far the 'Aussie flu' strain - which was circulating here last winter and led to a severe season of illness - is more aggressive this year.
Dr Oisin O'Connell, a respiratory consultant in the Bons Secours Hospital in Cork, said while the "virulence factor did not seem to be worse this year", he was seeing complications such as wheezing in patients.
There is also more bronchospasm with flu, which narrows the airways and affects the air coming in and going out of the lungs.
So far, the HSE has said the number of deaths from flu is "under 10".
But that is more due to a delay in confirmation of flu-related deaths. Next week there should be a clearer picture of how many lives it has claimed.
The weakness in our weaponry this year is the fact that the flu vaccine does not cover the B Yamagata strain that is now dominating.
However, it covers the other strains that are spreading - and even though the jab takes two weeks to kick in, it is still not too late to get it.
Dr Nuala O'Connor, a Cork GP, who was involved in the HSE's Undertheweather.ie website pointed out that the vaccine alone is not enough when it comes to reducing the risk of vulnerable people such as the elderly or cancer patients. "I emphasise the importance of creating a cocoon around people who will be at risk from the flu. That includes the importance of home helps and carers getting the flu vaccine," said Dr O'Connor.
If someone in the high-risk group gets the flu they should contact their GP and get an anti-viral drug within 48 hours. Others can stay at home and sweat it out, keep warm, take paracetamol or ibuprofen and drink plenty of water.
Although the public imagination is caught by more exotic viruses like Ebola and Zika, flu is our greatest risk and not to be underestimated. Around 90 people died of flu in Ireland last year. We will be in the grip of flu for another long stretch. It is not to be taken lightly and the onus is on everyone not to pass it on to others.