DUP leader Jeffrey Donaldson has said he has tested positive for Covid-19.
In a posting on Twitter, he said he had received a positive result from a PCR test.
"When I returned from London on Friday evening I felt a cold coming on but it has been getting worse," he said.
"PCR test has now come back positive. Close contacts will be notified. Thankfully I received my booster two weeks ago. The importance of being vaccinated cannot be overstated."
He added: "Work still goes on even though I'm a bit croaky. Sore throat is most uncomfortable symptom. I will still be having a virtual meeting with the Foreign Secretary @trussliz this afternoon on the need to remove the Irish Sea border which is reducing accessibility to medicines etc."
Today, Northern Ireland reported a further 2,096 cases of Covid-19 and three further deaths.
Stormont health minister Robin Swann said its geography will not separate it from the Omicron surge.
"We're already seeing an increase in numbers in the Republic of Ireland, we've always said in the past it's not a matter of if, it's when," he said.
1/2 When I returned from London on Friday evening I felt a cold coming on but it has been getting worse. PCR test has now come back positive. Close contacts will be notified. Thankfully I received my booster two weeks ago. The importance of being vaccinated cannot be overstated.
— Jeffrey Donaldson MP (@J_Donaldson_MP) December 21, 2021
"We are a number of days behind London and a number of days behind Scotland in regards to those cases, but we do expect to see an increase in our cases, we're already seeing a slight increase over the past number of days but vaccination will make the difference.
"We're still managing a high number of Delta variant cases, we expect Omicron to become the dominant variant, possibly this side of Christmas, and if not after Christmas."
Asked about people attending sporting events on 26 December, Mr Swann said the Covid certification scheme will cover those facilities.
"What I will say to anyone who is intending to go to one of those sporting events is follow the guidance, wear a face mask if you're travelling to it but also think about your activities around those sporting events.
"How you get there, how you get away from there, your activities before and after those sporting events, if they are outdoors follow the guidance and again make sure you come forward to get your vaccines and booster."
Meanwhile, Queen's University has said the majority of its classes in January will be delivered remotely due to the deteriorating Covid-19 situation.
The university made the decision as a "precautionary measure" having reviewed the "developing public health situation and taken some clinical advice".
In-person teaching will still be provided for technical classes such as lab sessions that cannot be delivered remotely.
The university's library, study spaces and support services will remain open.
Assessments scheduled for 4 January are set to proceed as planned "with enhanced social distancing in place".
