CANCUN, Mexico (AP) - As swine flu runs rampant in the Southern Hemisphere winter, world health experts are concerned that some hard-hit countries have been reluctant to take forceful measures to protect public health.

Only Friday did Argentina's new health minister, Juan Manzur, raise the country's official death toll to 44. He now estimates that as many as 320,000 people have been stricken with influenza, including about 100,000 with swine flu - a huge jump in what the government acknowledged previously, and an indication that Argentina's hospitals will remain overwhelmed for months.

Britain, for its part, had refused to do widespread testing for swine flu, slowing the World Health Organization's efforts to declare that the viral spread had become a pandemic. Britain's Health Minister Andy Burnham belatedly acknowledged Thursday that Britain needs to revamp its response and could see up to 100,000 new swine flu cases a day by the end of August.

The government was reluctant to implement unpopular measures leading up to last Sunday's midterm elections in Argentina. Now that they're over, it ramped up its response this week - doubling the winter vacation to a month for schools nationwide, sending pregnant women and other vulnerable workers home for 15 days and urging people to avoid crowds whenever possible.

But Argentina still refuses to declare a national public health emergency, despite ranking third in the world for swine flu deaths behind the United States and Mexico.

"An unfortunate situation in Argentina was this mix of elections and a pandemic, which we epidemiologists don't recommend," said Mirta Roses, director of the Pan American Health Organization, which has 25 experts working in Argentina this week.

Mexico, in contrast, deserves the whole world's thanks for its forceful, costly and very public response, which included a near-total shutdown of the nation's public life that cost the country $3.5 billion.

It helped slow the initial spread of the virus and gave other nations more time to prepare, said World Health Organization Director-General Dr. Margaret Chan.

"Mexico gave the world an early warning, and it also gave the world a model of rapid and transparent reporting, aggressive control measures, and generous sharing of data and samples," Chan said Thursday during a two-day summit of health ministers in Cancun.

Just how effective Mexico's draconian response was will take some time to determine, because scientists will have to compare what was done with what might have happened had the country done nothing, said Nancy Cox, who leads the influenza division of the U.S. Centers for Disease Control and Prevention.

"However, they were so courageous to do what they did. It impressed the entire world," Cox said.

Mexican President Felipe Calderon also faced resistance at home - he said some state officials wanted to hide the numbers for fear it would cause panic, but he overruled them. Mexico's toll has since risen to 10,687 cases, including 119 deaths.

"For many people across the world, Mexico was demonized precisely because it was providing truthful information," Calderon said.

The national shutdown in Mexico prompted Cuba and Argentina to cancel flights to Mexico and left a stigma that still hurts Mexico's all-important tourism industry. But Calderon said Mexico's reaction "allowed other countries to take preventive measures or activate their emergency programs."

Mexico's public health system also was overwhelmed initially, as doctors struggled to figure out how to fight the strange new virus.

Now they know that most patients survive if given proper treatment quickly, and that common seasonal influenza kills many more people. Even so, Argentina and Chile have struggled with huge caseloads.

"What's going on in the Southern Hemisphere really has lessons for everybody," said Dr. Keiji Fukuda, the WHO's top flu expert. "We have learned how important preparedness is."

But no amount of preparation can make up for systemic weaknesses, Cox said.

"If your health care system is already strained prior to the advent of a new disease that is causing a lot of infection in people, you are going to have tremendous problem with cases piling up," she said.

Chile has 7,342 confirmed swine flu cases, compared to 1,587 for Argentina, but only 15 deaths, in part because it had more antiviral drugs stockpiled and was able to respond more proactively. Argentina - already facing a huge caseload of bronchitis and common flu cases - hasn't had enough ventilators to treat everyone, Cox said.

"There are all these unexpected events that occur when you have a new pathogen, and some of these have played in the situation in Argentina," Cox said.

Australia has the most cases in the Asia-Pacific region - more than 4,568, including 10 deaths. Worldwide, the WHO said there were 337 deaths and more than 80,000 confirmed cases in 121 countries this week.

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AP Medical Writer Maria Cheng in London and Vicente Panetta in Buenos Aires contributed to this report.