More than 1,700 NI healthcare workers are isolating as a result of Covid-19.
The figures, from just three of the six health trusts, are a significant increase from a fortnight ago when BBC News NI reported that 1,200 staff were isolating across all the trusts.
NI’s two other health trusts and the ambulance service have been asked for their latest figures.
An emergency department nurse said the situation was “getting worse”.
“From a staffing point of view, we are stretched,” said Aron Sturdy, who works at the Ulster Hospital in Dundonald.
“We don’t know what we are facing in terms of our workload because our staff and team numbers change from one day to the next and can be quite dramatic.
“It’s all boiling down to sickness, stress – everything else is just weighing down on the staff and they can’t be blamed for it.”
There have been three more Covid-19 related deaths reported by the Department of Health, bringing the total death toll to 624.
There have also been 913 further positive cases, bringing the total number of cases to 28,953.
The Belfast Health and Social Care Trust has confirmed that 1,108 of its staff are isolating for reasons associated with Covid-19.
A total of 393 are symptomatic and a further 375 have been contact traced, the trust said.
“Any increase in staff absence has the potential to impact on service delivery and we will continue to monitor this,” the trust said in a statement.
“Where there is an absence as a result of self-isolation and, where possible and depending on their role, the trust has been facilitating staff working from home.
“Symptomatic staff or family members they live with can book a test at our Knockbracken site through a central booking number.”
The Southern Trust, which operates Craigavon Area Hospital and is the smallest of the trusts in Northern Ireland, has 505 staff on leave as a result of the virus.
This includes 207 who are symptomatic, 68 who have a symptomatic family member and 165 who are isolating as a result of contact tracing.
In a statement, a spokesman said: “At this stage of the pandemic, when Covid-19 is surging so rapidly in Northern Ireland, the trust is managing high numbers of Covid-19 cases and clusters on several sites.
“We continue to follow national guidance in managing these incidents and we report and manage identified clusters in line with the guidance.”
The South Eastern Trust has recorded 157 staff isolating.
Ulster Hospital nurse Mr Sturdy said he believed measures being put in place would help alleviate some of the pressures but he added that the public also had a part to play.
He added: “The Downe (Hospital) re-opening will hopefully take some weight of the shoulders of the Ulster Hospital.
“It’s about asking the general public engage with all the services; with their GPs and with everything that’s being made available to them and to try and lessen that load that’s hitting the emergency departments.”
In Londonderry, a GP has said the Covid centre at Altnagelvin Hospital has been “like a war zone”.
Dr Paul Molloy said the facility was seeing almost as many patients in a day now as it did in a week during the months of March and April.
More than 20 patients were being treated at the unit on Monday evening, he said.
The Western Trust said there are currently 72 patients in the hospital with coronavirus and that it had moved into a “further ward to facilitate increased Covid-19 admissions” on Monday.
The Derry and Strabane District has NI’s highest infection rate, with 770 cases per 100,000 people, according to the Department of Health.
Dr Molloy told BBC Radio Foyle that he used the war zone comparison in a social media post on Monday to make sure “people know Covid is out there”.
Dr Molloy said the Covid centre is coping but warned it was vital people adhered to the public health guidance.
“Covid is there, and very prevalent in our community. Irrespective of what the government is doing, irrespective of what the lockdown rules are, everybody needs to be very careful,” he said.
The Western Trust said that it had activated the “level red” stage of its Covid surge plan and that it was a “very worrying time”, with the number of patients needing admission doubling “every three to four days”.
“If the rate of infection continues locally, we will have some very difficult decisions to make in the coming days around what services we can continue to offer,” it said.
“The increase in community transmission has also had a knock-on effect on staffing levels, with many staff not being available to us as they have had to self-isolate.
“We really need the public to act now and follow the public health messaging and help us to get the level of transmission down.”