A swine flu-related death has been reported in Washington state, bringing the total number of fatalities in the United States to three, FOX affiliate KCPQ confirmed.
The latest victim was described as a man in his 30s with underlying heart conditions.
The unidentified Snohomish County man died Thursday from what appears to be complications from the H1N1 virus, the state Department of Health said in a statement.
In addition to the heart conditions, the man had viral pneumonia at the time of his death, but swine flu was considered a factor in his death, the statement said.
The man reportedly began showing symptoms on April 30.
"This death is tragic," said Washington Gov. Chris Gregoire. "Our thoughts are with those affected by this man's passing. It's a sobering reminder that influenza is serious, and can be fatal. ... Our public health agencies are doing everything they can to track and monitor this outbreak and to protect the people of our state."
His death and the death of a 53-year-old man in Costa Rica on Saturday brings the global death toll to 53, including 48 in Mexico, three in the United States and one in Canada.
Earlier Saturday, the Centers for Disease Control and Prevention said the U.S. had 2,254 confirmed cases of the H1N1 swine flu in 44 different states.
"Today there are almost 3,000 probable and confirmed cases here in the United States," the CDC's Dr. Anne Schuchat told a news briefing, according to a Reuters report. "The good news is we are not seeing a rise above the epidemic threshhold in that system."
In addition to the three who have died here from the illness, 104 are currently hospitalized.
Like other deaths outside Mexico, the Costa Rican man suffered from complicating illnesses, including diabetes and chronic lung disease, the Health Ministry said.
Previously, U.S. authorities reported swine flu deaths of a toddler with a heart defect and a woman with rheumatoid arthritis, and Canadian officials said the woman who died there also had other health problems but gave no details.
In Mexico, where 48 people with swine flu have died, most of the victims have been adults aged 20 to 49, and many had no reported complicating factors. People with chronic illnesses usually are at greatest risk for severe problems from flu, along with the elderly and young children.
The Costa Rican fatality was one of eight swine flu cases in the country confirmed by the U.S. Centers for Disease Control and Prevention, Health Minister Maria Luisa Avila told The Associated Press.
Avila said officials had been unable to determine how the Costa Rican patients became infected, but she said he had not recently traveled abroad. Many flu sufferers in other nations have been linked to recent trips to the United States or Mexico.
Mexico, which raised its count of confirmed cases to 1,626 based on tests of earlier patients, continued to gradually lift a nationwide shutdown of schools, businesses, churches and soccer stadiums.
But an upswing in suspected — though not confirmed — cases in parts of Mexico prompted authorities in at least six of the country's 31 states to delay plans to let primary school students return to class on Monday after a two-week break.
"It has been very stable ... except for those states," Health Department spokesman Carlos Olmos said, referring to states in central and southern Mexico.
Mexican health authorities released a breakdown of the first 45 of the country's 48 flu deaths that showed that 84 percent of the victims were between the ages of 20 and 54. Only 2.2 percent were immune-depressed, and none had a previous history of respiratory disease.
In Japan, authorities quarantined a high school teacher and three teenage students who tested positive in an airport test for swine flu after they returned from a school trip to Canada. Officials said they were working with the World Health Organization to contact at least 13 people on the flight who had gone on to other destinations.
Japanese Health and Welfare Minister Yoichi Masuzoe acknowledged it would be difficult to trace everyone who came into contact with the infected Japanese, who visited Ontario on a home-stay program in a group of about 30 students. The three were isolated and recovering at a hospital near Narita International Airport.
"There are limitations to what we can do, but we will continue to monitor the situation and strengthen or relax such measures as needed," he told reporters.
Public broadcaster NHK TV urged people who were aboard the same Northwest Airlines flight from Detroit to call a special telephone number for consultations. So far, 49 people had been traced and would be monitored for 10 days, officials said.
Australia reported its first case Saturday in a woman it said was no longer infectious. She first noticed her symptoms while traveling in the U.S., federal Health Minister Nicola Roxon told reporters.
New Zealand — the first country in the Asia-Pacific region to confirm cases — reported two more Saturday for a total of seven. The two high school students returned last month from a school trip to Mexico. Six of the country's cases were in students and a teacher on that trip; the seventh traveled on the same plane as the group.
Norway's National Health Directorate reported that country's first two confirmed cases: a man and a woman, both aged 20, who had been studying in Mexico.
In Canada, officials said almost 500 hogs quarantined on an Alberta farm after being diagnosed with swine flu had been killed because animals were becoming overcrowded since the facility was barred from shipping any to market.
"They were not culled for being sick. They were culled because of animal welfare concerns," Dr. Gerald Hauer, the province's chief veterinarian, told reporters. He said about 1,700 pigs remained on the farm.
Authorities have said the pigs apparently became infected from a farm worker who had been in Mexico. Experts say people cannot catch flu from eating pork, but in rare cases people have been infected by contact with a live pig.
The Associated Press contributed to this report.