Four new cases of Covid-19 have been detected in Northern Ireland.
They are adults and the illnesses are connected to recent travel to northern Italy, health authorities said.
The total with the infection has risen to 16.
On Tuesday evening, Irish League football team Linfield FC announced that one of its players had tested positive.
Earlier, Chief medical officer Michael McBride told a media briefing: “It is a question of when, not if, we see community transmission in Northern Ireland.”
Community transmission means a patient has not been to an affected area like China or Italy or had close contact with someone who contracted the disease there.
Stormont leaders have cancelled a St Patrick’s trip to Washington DC amid the coronavirus outbreak.
First Minister Arlene Foster and Deputy First Minister Michelle O’Neill are to remain in Northern Ireland to focus on efforts to contain the spread.
The Deputy First Minister & I have decided not to travel to Washington for the St Patrickâs Day receptions. Whilst it is an enormous opportunity to showcase Northern Ireland in DC, our priority is dealing with the spread of Coronavirus. We will attend the cobra meeting tomorrow.— Arlene Foster (@DUPleader) March 10, 2020
A call centre in Belfast was forced to close on Tuesday for a deep clean after a staff member contracted the virus.
Nobody with a serious underlying disease has yet fallen victim and Dr McBride said people need to take sensible steps to protect themselves rather than panicking.
Medics are still attempting to contain the disease’s transmission.
Gerry Waldron, from the Public Health Agency in Northern Ireland, said: “The risk is out there and the risk is growing, unfortunately, of coming in contact with Covid-19.”
Conall McCaughey, a virologist involved in the testing process, said numbers conducting the test for the genetic sequence associated with the infection had been increased and would be boosted further.
Retired GPs are also due to be enlisted to help delay the illness’s march.
Mr McCaughey said: “The numbers will clearly increase and we will have to adapt to that and have done considerable amounts of planning.”
Mrs Foster and Mrs O’Neill had already cancelled the New York leg of their itinerary in the US.
They will also now miss a series of engagements in the US capital, including the traditional St Patrick’s reception with President Donald Trump in the White House on Thursday.
On Monday, Taoiseach Leo Varadkar also cancelled plans for the New York leg of his St Patrick’s itinerary, but still intends to travel to Washington.
Mrs Foster tweeted: “The Deputy First Minister & I have decided not to travel to Washington for the St Patrick’s Day receptions. Whilst it is an enormous opportunity to showcase Northern Ireland in DC, our priority is dealing with the spread of Coronavirus. We will attend the cobra meeting tomorrow.”
Ms O’Neill said: “We remain in containment stage, however as leaders of the executive we have decided to suspend our travel to the United States this week since our full attention is on civil contingency planning around the coronavirus outbreak and protecting public health.
Speaking to the media on my decision to suspend travel plans to Washington DC tomorrow.— Michelle OâNeill (@moneillsf) March 10, 2020
We have decided to suspend our travel to give our full attention to civil contingency planning around the Coronavirus outbreak and protecting public health. pic.twitter.com/89jluuQdou
“We are fully engaged in the Cobra meetings alongside England, Scotland and Wales in assessing the response to the outbreak on advice from our chief medical officer.
“There is all-Ireland co-ordination between health and medical professionals on a daily basis also. I am in regular contact with Tanaiste Simon Coveney and health ministers north and south are also working closely.
“It is regrettable that we must suspend our travel to the US to meet with political leaders and potential investors, but it is necessary.
“We were going to deliver the message that the north is open for business and is a great place to invest.”
After announcing one of its players had been diagnosed with the virus, Linfield FC said: “This club is taking advice from the relevant authorities and will provide an update when we have further details.”
Club chairman Roy McGivern tweeted: “Very unpleasant news that one of our players has tested positive for Covid-19.
“The priority now is to look after the welfare of our players and staff. Issues around football will be addressed in due course.”
Around 1,000 people work at the virus-impacted Halifax call centre in the Gasworks area of Belfast city centre.
It is understood staff have been asked to self-isolate or work from home or from a contingency site.
Lloyds Banking Group, which owns Halifax, said: “The Belfast Gasworks building has been temporarily closed to allow for the appropriate areas of the site to be cleaned, after a colleague based there was diagnosed with Covid-19.
“Our priority is the wellbeing of the individual, as well as the colleagues and visitors to the building. We’re closely monitoring the developing situation and continue to follow official guidelines.”
Two schools in Co Armagh are already closed for deep cleaning after a young person was diagnosed with Covid-19.
Newtownhamilton High School and primary school share the same site in Co Armagh and are expected to reopen next week.
Several sports clubs have also had to take precautionary steps after individual members tested positive.
St Patrick’s Day festivities in Belfast are among events which have been axed amid efforts to contain the spread of the virus.
Dr McBride said: “There is the public perception and maybe the expectation of some of these steps being taken but we need to be guided by the science.
“If we start to take measures such as that, which will have a huge social and economic impact which the evidence is that they are going to have limited benefit, then really we should not be making those interventions.”
On Monday, Stormont Health Minister Robin Swann warned that between 50% and 80% of the population could contract the coronavirus in a worst-case scenario.