FREDERICTON -- Health officials in New Brunswick say there are still only two confirmed cases of measles in the Saint John region after a third suspected case tested negative.

Dr. Jennifer Russell, the chief medical officer of health, said there was some confusion about whether there were four cases after the New Brunswick Community College reported a suspected case on Thursday that her office was already investigating.

"The case they were talking about was the same case that we were talking about," Russell told reporters on Friday.

"That person does not have measles."

She said the two people with the highly contagious infection remain in isolation at home. Russell previously confirmed the first two cases were related.

The first confirmed case involved a person who visited the Halifax Infirmary emergency room last month and later went to the ER and X-ray room at Saint John Regional Hospital. Officials have confirmed the first infected patient recently travelled internationally.

The second case was recently confirmed at Kennebecasis Valley High School.

Health authorities say the person ate lunch at Shadow Lawn restaurant in Rothesay, N.B., on May 6 and attended the John Cleese show at Harbour Station on May 7.

Russell is now urging anyone who sat in sections 26 and 27 during the Cleese show, and were born between 1970 and 1995, to attend an immunization clinic at Saint John's Exhibition Park next Wednesday and Thursday.

"I cannot stress enough that this is only for people born between 1970 and 1995 who attended the John Cleese event at Harbour Station on May 7 and sat in the sections that I just mentioned," she said.

Russell said immunization is required because people born during that time period typically received only one dose of the vaccine for measles when two are recommended. Anyone born before 1970 or who has already had the measles are considered immune.

She said the appearance of measles in the Saint John area is considered a regional outbreak and she added that anyone who thinks they may have the virus should stay home and contact the province's 811 Tele-Care number for further advice.

"Do not go directly to the ER," Russell cautioned.

She said she knows New Brunswickers are worried about the outbreak and health officials understand the situation.

"Our focus at this time is the Saint John region and for residents outside this region information for immunization clinics will be announced at a later date once we have addressed the immediate outbreak in Saint John."

New Brunswick wasn't the only jurisdiction dealing with the measles on Friday, after health authorities in Montreal launched a public appeal in an attempt to curb a possible outbreak there.

Seven cases of measles have been reported in Montreal since the beginning of the year, with the first five involving exposure to the disease outside country.

The measles infection can be prevented with a vaccine. Most people who contract the virus make a full recovery.