ieExplains: Here's what you need to know about the new flu strain in Ireland 

The winter flu season has started earlier than usual in Ireland, with 'highly virulent' new strain — H3N2 subclade K — causing concern

The flu vaccine is available from GPs and pharmacies and is free to those aged 60 or older, children aged from two to 17, and if you are a healthcare worker or pregnant.

The winter flu season has started earlier than usual in Ireland and doctors are urging people to get vaccinated.

A "highly virulent" new strain — H3N2 subclade K — is causing increased concern. Here's what you need to know.

What is subclade K?

The new flu strain is H3N2 subclade K, and it has undergone several mutations that would not have been previously found in flu viruses.

According to the European Centre for Disease Prevention and Control (ECDC), the newly-emerged strain has now been detected on all continents.

Dr Scott Walkin, antimicrobial resistance and infection control clinical lead at the Irish College of GPs, said the strain was "highly virulent" and "H3 flu tends to be more severe than other types".

The early onset of flu season and the emergence of subclade K led the ECDC to issue a threat assessment brief to raise awareness. It said considerable uncertainty remained around the likely public health impact of this subclade on the influenza season.

It said the H3N2 virus had not been the dominant virus in recent seasons, which may lead to lowered immunity in populations without recent exposure. However, the ECDC said it was still important to get vaccinated.

“Even if a less well-matched A(H3N2) virus dominates this winter, the vaccine is still expected to provide protection against severe disease, so it remains a vital public health tool,” the ECDC pointed out.

Dr Walkin said the "winter flu season has arrived several weeks earlier this year". 

Already, even though the season is just starting, seven people have died, and admissions to hospitals have increased by 50% between week 46 and week 47.

Dr Walkin said the flu vaccine provided "good protection" against severe disease.

"The vaccine is effective within two weeks of getting it, so it’s really important to get the vaccine now to ensure it doesn’t ruin your Christmas or someone else’s."

What are the symptoms?

The new flu strain does not appear to have different symptoms to other types of flu, but they may appear more severe.

The HSE says flu symptoms can come on very quickly and can include:

• Sudden high temperature of 38C or above;
• Severe body aches and pains;
• Extreme tiredness; 
• Persistent dry cough; 
• Headache; 
• Sore throat;
• Runny or stuffy nose; 
• Loss of appetite; 
• Difficulty sleeping; 
• Diarrhoea or tummy pain. 

According to HSE, the flu symptoms are similar for children, although they can also get a pain in their ear, and seem to be less active.

How many cases of flu have there been in Ireland? 

As reported in the Irish Examiner this week, HSE chief clinical officer Dr Colm Henry said hospitals were seeing "a rapid increase of cases of patients with influenza, including those needing hospitalisation".

“Four hundred and eighteen cases were reported in hospitals the week ending 29 November compared to just 213 the week before,” Dr Henry said.

He said the numbers indicated health services would face significant pressures this winter

How do I get the flu vaccine? 

The flu vaccine is available from GPs and pharmacies and is free to those aged 60 or older, children aged from two to 17, and if you are a healthcare worker or pregnant.

How to treat the flu at home?

The HSE advises people to take a number of steps to help ease symptoms and get better more quickly.

These include:

• Bed rest and sleep;
• Keep warm;
• Take paracetamol or ibuprofen to lower your temperature and treat aches and pains;
• Drink plenty of water to avoid dehydration (your pee should be light yellow or clear).