A quarter of the Northern Ireland Ambulance Service are off work sparking longer waiting times even for the most ill patients.
Some 221 workers are off due to Covid-19, with another 155 of the 1,496 workforce off for non-Covid reasons.
NIAS chief executive Michael Bloomfield said while the sickest patients are prioritised, as waiting times get longer, there have been instances where they have had to advise callers to, where possible, make their own way to hospital.
Thousands of workers across the health service in Northern Ireland are absent from work due to Covid-19.
The figures come as the Omicron variant sparks the highest case numbers since the start of the pandemic in March 2020.
Chief scientific adviser Professor Ian Young has estimated the peak of the wave is yet to come, expected between early to mid January.
Data provided by the health trusts and NIAS to the PA news agency on Wednesday indicated that over 4,000 workers were absent due to the virus.
In the Belfast Health Trust, some 1,220 staff were recorded on Tuesday as absent due to Covid-19.
Another 1,735 of the 21,379 workforce were absent due to non-Covid reasons bringing the proportion absent to 14%.
On Wednesday, there were 1,069 staff absent due to Covid-19 in the Southern Health Trust, as well as 331 of the 12,575 workforce for non-Covid reasons bringing the proportion absent to 11%.
On the same day there were 802 staff at the South Eastern Trust absent due to Covid-19, and 526 of the 11,353 workforce absent for non-Covid reasons bringing the proportion absent to 12%.
In the Northern Health Trust there were 489 absences due to Covid-19 on Wednesday.
Another 784 of the 12,170 workforce were absent for non-Covid reasons bringing the proportion absent to 10%.
In the Western Health Trust there were 874 absences due to Covid-19.
Another 1,218 of the 11,477 workforce were absent for non-Covid reasons bringing the proportion absent to 18%.
Mr Bloomfield said absences are expected to rise higher still as the peak of the Omicron wave is reached.
“Services right across the health and social care system are already under significant pressure and unfortunately that is likely to worsen in the coming weeks if the number of staff unavailable for work increases as it is expected to do as we reach the peak of this current surge,” he said.
“From an ambulance service point of view that means as always we continue to try to focus the resources we do have available on the sickest patients but we are now seeing the response times even for those most clinically urgent calls are now taking much longer and indeed there are some patients who whenever they phone in we have to tell them that it is highly unlikely we will get them in an ambulance any time soon and if they are able to make their own way to hospital with a family member, that they should do that.”
He said across the health service he is aware of particular challenges in domiciliary care, mental health services, and emergency departments which he described as “extremely busy”.
“As staff are at the heart of providing every single element of health and social care services, as we see more staff affected by this, regrettably it is and will impact on every part of hospital and community services,” he said.
Mr Bloomfield said many of NIAS continency plans are being used on a daily basis, such as redeploying staff into frontline services, reduction in training and other actions including assistance from other emergency services.
He said the situation is “extremely difficult for staff”.
“It no longer feels adequate to simply say staff are exhausted, people have been saying that for a long time, but it is the case, they are asked time and time again that there is a new surge, each time it feels more difficult,” he said.
“Currently with the high number of staff affected by this, that places an even larger responsibility on those staff who are at work to work additional shifts etc.
“They’re tired, they are upset that they’re not able to provide the level of care that they want to for patients and they know that patients need, and they are finding it very very difficult and while I know I can rely on them to continue to step up and do the best they can, I don’t know how much longer we can continue to expect them to do that.”