HALIFAX -- New Brunswick has reported its third new case of COVID-19 in the last week and all are in a single cluster connected to a health-care worker at the Campbellton Regional Hospital who failed to self-isolate after travelling to Quebec.

"These cases are linked to someone who travelled back to New Brunswick and did not self-isolate. The case involved a health-care worker who saw patients and also worked at the Campbellton Regional Hospital," said Dr. Jennifer Russell, New Brunswick's chief medical officer of health, during a news conference in Fredericton Wednesday afternoon.

The other two active COVID-19 cases are someone under the age of 19 and someone in their 90s. They are both linked to the health-care worker, in their 50s, who travelled to Quebec for personal reasons.

New Brunswick Premier Blaine Higgs said there are rules in place and they must be followed and now, because of "one irresponsible individual," a number of patients at the Campbellton Regional Hospital might have been exposed to the virus. The health-care worker saw "multiple patients" over a two-week period.

"We are still contact tracing, but we know this zone is currently at a higher risk due to actions of one irresponsible individual," Higgs said. "We know we'll see more cases connected to this."

Higgs says the person was not "forthcoming about their reasons for travel upon returning to New Brunswick," which means they wouldn't have been advised at the border to self-isolate, but both Higgs and Dr. Russell asked New Brunswickers to use a little common sense. For two months, anybody who has travelled outside the province has been asked to self-isolate for two weeks.

"Unfortunately, not everyone is taking this seriously," Dr. Russell said. "It is very important that people be truthful with public health staff."

Dr. Russell says the investigation into the situation is underway. She won't say if there will be repercussions for the individual, but the premier was more blunt.

"If charges need to be laid, they will," Higgs said. "We don't have all the facts, but over the coming days, we will get them."

Higgs reminded the public of their responsibility to follow public health directives to ensure a safe reopening of the province.

"By pushing against restrictions, you are endangering not just yourself, but your family, friends and fellow New Brunswickers," said Higgs. "Now is not the time for New Brunswickers to take unnecessary risks, which could undo all the hard work it took to get us to this point."

Later Wednesday evening, the Vitalite Health Network said the Campbellton Regional Hospital is closing its emergency department and cancelling all non-urgent or elective services for 24 hours because of a "high risk of transmission of COVID-19."

In a news release, Vitalite said the measure was needed "to limit transmission of the virus originating from a member of the facility's health care staff."

"We know that this decision will inconvenience the communities of the Restigouche and surrounding areas.However, the health and safety of our staff remain our priority. We must do everything in our power to limit the risk of spread," said Gilles Lanteigne, the president and CEO of Vitalite Health Network.

Dr. Russell said, to slow the spread of COVID-19 in Zone 5 (the Campbellton region), she is immediately restoring the restrictions that were removed last week -- but only in Zone 5.

That means that all businesses that reopened last week and all activities that became permissible must close or stop as the area returns to the so-called "orange level" -- or the first phase of the removal of pandemic restrictions.

"I strongly encourage people to stay at home (in that region), and to stay in that zone as much as possible," Higgs said.

Zone 5 extends from Whites Brook to the Village of Belledune, including Tide Head, Atholville, Campbellton, Dalhousie, Eel River Dundee, Eel River Bar First Nation, Balmoral, Charlo and Belledune.

Higgs says this situation could have happened without reopening and called it "most concerning."

Dr. Russell also said that any New Brunswickers who have travelled to the area should monitor their health. She said that anybody who has travelled there should seek testing even if they are not showing symptoms.

"We cannot afford to take chances with this virus," Dr. Russell said. "This is a global pandemic and it's not going to end until we have a vaccine. This virus does not move by itself; it moves with people. People can spread the virus even if they don't have symptoms."

Lanteigne encouraged all New Brunswickers, but particularly those in the Campbellton region to follow the public health recommendations.

"We cannot let our guard down.The third case being announced today is proof of that." Lanteigne said. "We must remain vigilant and work together to keep ourselves and others safe. Our battle is not over. Indeed, it has just begun."

New Brunswickers can also use an online self-assessment tool to help determine if they should be tested for COVID-19.

Higgs said that, starting Thursday, there will be mobile testing in the region.

"We have to control this within the region," Higgs said.

Until now, Zone 5 has had the least number of tests processed, but that will change over the next two weeks.

As public health officials begin to trace contacts of all the people who have recently been diagnosed, Dr. Russell is advising New Brunswickers to "rethink how many close contacts" they have.

The new case brings the province's overall total to 123. The first 120 all recovered before the Campbellton cluster emerged.