Canada became the third country to confirm human cases of swine flu with public health officials reporting six people falling ill in Nova Scotia and British Columbia, all of them linked to people who had traveled to Mexico.

Dr. David Butler-Jones, Canada's Chief Public Health Officer, said all have recovered and are doing well.

"These are probably not the last cases we'll see in Canada," Butler-Jones said.

Dr. Danuta Skowronski of the British Columbia Centre for Disease Control said the six cases were all mild and no one required hospitalization.

She said the two people stricken in the Pacific province had links to travel to Mexico and have been asked "self-isolate" but have not been quarantined. Public health officials in Nova Scotia said the four cases in the east coast province also were linked to travel to Mexico.

Official said all six cases are same strain as the one found in Mexico.

Nova Scotia Chief Public Health Officer Dr. Robert Strang said four students from King's-Edgehill School ranging in age from 12 to 17 or 18 are recovering from what he described as "very mild" cases of swine flu that did not require hospitalization.

"It was acquired in Mexico, brought home and spread," Strang said of the Nova Scotia cases.

The World Health Organization has declared swine flu to be a "public health emergency of international concern."

Mexico's health minister says the disease has killed up to 86 people and likely sickened more than 1,400 in the country since April 13.

U.S. health officials said Sunday that 20 swine flu cases have been reported so far in New York, Ohio, Kansas, Texas and California. Patients have ranged in age from 9 to over 50. At least two were hospitalized. All recovered or are recovering.

"At this point we're not seeing severe cases like that occurring in Mexico. We're consistent with the United States who are seeing very mild illness from the swine flu," Strang said.

Dr. Gaynor Watson-Creed, a doctor in a Nova Scotia clinic, said students from King's-Edgehill took part in a class trip to Mexico's Yucatan Peninsula earlier this month and "probably came into contact with the flu" there and spread it to others when they returned. Health officials said between 20 and 23 students from the school traveled to Mexico from April 1-8.

Joe Seagram, headmaster of the school, said 17 students and four staff at the school are in isolation and will be for seven days or until they are symptom free. Only four have confirmed cases.