The public are being asked not to attend the emergency department at Cork University Hospital unless absolutely necessary as it struggles with the ongoing impacts of the HSE cyber attack.
Heading in to the bank holiday weekend, emergency consultant Professor Conor Deasy asked the public to retain the emergency departments for emergencies.
Prof Deasy said the last three weeks have been extremely difficult for patients and all staff, with extreme delays and ongoing concerns about patient safety.
Speaking on RTÉ's Morning Ireland, he said "this is far more challenging than Covid, which hasn't gone away either".
He asked patients with non-urgent concerns to attend a GP out of hours service, a local injury unit or a local pharmacist.
Some patients are waiting up to 12 hours to be seen by a doctor as staff continue to use manual systems, he said.
"The impact on our ability to provide safe care in any sort of a timely way is really compromised", he said.
"If we were an airline we would be grounded, shut down, we couldn't be allowed to fly ... but we are a hospital and have to keep vital services going and keep delivering emergency services."
Prof Deasy said some of the increase in demand is linked to the Covid-19 vaccination programme, with many people presenting with post-vaccination symptoms.
There is "no question" that negative publicity has caused people to be "hyper-aware and concerned" about any symptoms that they may have, he said.
He said that he has yet to see anyone requiring hospital admission as a result of the vaccine and sought to reassure people, saying "this vaccine is safe and far safer than enduring Covid".
