The Department of Health has warned that up to 1m people could become infected with swine flu in Ireland over the autumn and winter.
The department's Chief Medical Officer, Dr Tony Holohan, has sent a letter to GPs and other medical professionals warning them that up to 25% of the population could catch the influenza A (H1N1) swine flu virus.
Dr Holohan said this would put significant strain on family doctors, hospitals and intensive care facilities.
The letter was co-signed by the National Director of Population Health, Dr Patrick Doorley.
So far 144 people in Ireland have contracted swine flu.
Elsewhere, the World Health Organisation is now warning that the virus is unstoppable.
WHO Director General Dr Margaret Chan has also indicated the availability of a vaccine may be further away than had been anticipated.
Information from clinical trials will not be available for another two to three months and experts said a vaccine may not be generally available until October.
