The HSE is advising people to consider all medical options before attending an emergency department.
It said hospitals and staff are dealing with high levels of patients with flu, Covid and RSV and are causing serious pressure on health infrastructure.
"As expected, Emergency Departments are becoming extremely busy due to the unprecedented combination of very high levels of flu, COVID-19 and other respiratory illnesses in the community," said the HSE's Chief Operations Officer, Damien McCallion.
"Those who believe they may be seriously ill and require emergency care should of course come to hospital, but we would urge others to consider seeking support from pharmacists, GPs, GP Out of Hours Services and Minor Injury Units.
"These services have emergency responses in place for patients presenting with respiratory and other urgent health issues."
The Health Service also say "while this surge...was predicted," it is following the most pessimistic model forecasted and appears to be accelerating quicker than expected.
It comes as individual hospitals were advising patients with non-urgent care needs to avoid attending emergency departments.
All out-patient appointments for University Hospital Limerick have been cancelled with only urgent elective surgeries going ahead at the hospital "over the coming days."
The Mater Hospital in Dublin is also urging people with non-urgent conditions to avoid coming to its Emergency Department.