MEXICO CITY (AP) — European countries have been using antiviral drugs much more aggressively than the United States and Mexico to combat swine flu — a difference in strategy that could have a big impact as the virus that is already linked to 63 deaths spreads around the planet.

The World Health Organization recommends the U.S. and Mexican approach — saving Tamiflu and Relenza for those patients most at risk.

\”European countries, which are mainly importing the cases, have been using antivirals very aggressively,\” WHO medical expert Dr. Nikki Shindo said Tuesday. \”Countries like Mexico and the United States, they are trying to save the treatment for patients with underlying conditions and also the other groups at increased risk, such as pregnant women.\”

Each country\’s health experts must decide if infected people should immediately be treated with antivirals, Shindo said — a decision that also must take into account how many antivirals are available in each country. \”As part of pandemic preparedness plans we urge countries to plan for prioritization.\”

In the U.S. — where one pregnant woman with swine flu died and 20 of the 116 hospitalized cases are pregnant — experts are recommending Tamiflu for pregnant women with confirmed swine flu infections.

Dr. Anne Schuchat of the Centers for Disease Control and Prevention said risks from the virus are greater than the unknown risks to the fetus from the drugs Tamiflu and Relenza.

Pregnant women don\’t catch swine flu any more often than other people. But when they do, they are more likely to suffer dehydration and pneumonia. The flu also raises their risk for a premature birth.

The WHO also recommends that antivirals be targeted mainly at people suffering from additional disease and at pregnant women. For most infected people, the symptoms have been mild so far, so the majority of patients do not need hospitalization or antiviral therapy, Shindo said.

The swine flu virus spread to more countries Tuesday, but at the center of the epidemic, Mexican health officials said the worst is over despite a rising death count.

Mexico\’s toll rose to 58 deaths and 2,282 confirmed cases of swine flu — a rise of two deaths and 223 more cases since Monday — but Health Secretary Jose Angel Cordova said this reflects a testing backlog: The last confirmed case was May 8.

The more cases Mexico confirms, the less deadly the virus appears, Cordova said. And 92 percent of people sickened or killed in Mexico showed symptoms \”before we knew that we were fighting against a new germ,\” and knew how to properly treat them, he added.

With the virus now spreading worldwide, Swiss pharmaceuticals company Roche Holding AG announced it is donating enough Tamiflu for 5.65 million more people to the WHO.

The donation will replenish a stockpile of 5 million treatments given to WHO by Roche in 2005 and 2006. The agency shipped those supplies to poor countries. A further 650,000 packets containing smaller doses of the drug will be used to create a new stockpile for children.

Thailand and Finland reported their first confirmed swine cases Tuesday, of people just arrived from Mexico.

Cuba also confirmed its first case — a Mexican student attending a Cuban medical school — despite imposing strict restrictions on flights and travelers from Mexico in hopes of keeping the virus off the island. The case prompted Fidel Castro to accuse Mexico of hiding the epidemic until after President Barack Obama visited last month.

\”Mexican authorities did not inform the world of the presence (of swine flu), while they waited for Obama\’s visit,\” he wrote, although Obama\’s April 16 visit came a week before Canadian and U.S. scientists identified swine flu in Mexican patients. The laboratory match prompted Mexico to quickly impose an unprecedented shut down of most aspects of public life for days.

Cordova said that \”there has never been any concealing of information\” from world health officials, and that he had no plans to explain Mexico\’s response to Cuba. \”I\’m not going to send anything to Fidel Castro, nor has he asked me to.\”

China said it has tracked down and quarantined most passengers who shared flights with the mainland\’s first known swine flu sufferer — a Chinese graduate student who is said to be improving. The man studied at the University of Missouri.

While officials at the university advised people not to panic and to simply keep up basic hygiene, China\’s leaders said they would strengthen disease monitoring systems.

\”We must attach great importance to the fact that the flu epidemic is still spreading in some countries and regions, and that China has discovered one case,\” said President Hu Jintao.

About 260 people were quarantined in Beijing, including 70 foreigners, the China Daily reported. In Sichuan province, the government said another 95 people who had flown with the man from Beijing to the southwestern provincial capital city of Chengdu were being isolated.

The WHO has confirmed thousands of swine flu cases in 33 countries. The United States has the most — 3,009 — according to the U.S. Centers for Disease Control and Prevention, followed by Mexico and 330 in Canada. Along with those who died in Mexico, swine flu has contributed to the deaths of three people in the U.S., one in Canada and one in Costa Rica.

A study released Monday by the journal Science suggests there are many more cases than those confirmed by laboratories — anywhere from 6,000 to 32,000 cases in Mexico alone by April 23, the day the epidemic was announced.

Researchers also said this swine flu is appears to be substantially more contagious than normal, seasonal flu, and kills between 0.4 percent and 1.4 percent of its victims. But lead author Neil Ferguson of Imperial College, London, said the data remain incomplete: \”It\’s very difficult to quantify the human health impact at this stage,\” he said.

Cordova said Mexico\’s shutdown of schools — lifted Monday in most of the 31 states — had averted an avalanche of cases. \”It would have been difficult for us to have controlled this epidemic,\” said Cordova.

Mexico\’s overburdened health system has been strained by the epidemic. Dozens of government doctors and nurses marched and blocked streets in the Gulf coast city of Jalapa to demand higher pay and better working conditions.

Mexico also is trying to revive its economy after the epidemic pummeled tourism, the country\’s third-largest source of legal foreign income.

Cordova said there have been no swine flu cases in five top Mexican vacation spots, including Los Cabos, Puerto Vallarta, Cozumel, Mazatlan and Zihuatanejo.

\”The tourist destinations are safe in Mexico,\” he said. \”People can return to them with peace of mind.\”

But with incoming flights virtually empty of tourists, Tourism Secretary Rodolfo Elizondo announced a $90 million publicity campaign to urge Mexicans to vacation at home. He said promoting trips by foreigners now \”would be like throwing money away.\”

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Associated Press writers Michael Stobbe in Atlanta; Olga Rodriguez and Alexandra Olson in Mexico City; Miguel Angel Hernandez in Veracruz, Mexico; Maria Cheng in London; and Gillian Wong in Beijing contributed to this report.