| MEXICO CITY
MEXICO CITY Mexico's flu outbreak appeared to be stabilizing on Saturday but officials warned the unpredictable virus still threatened a global pandemic.
Mexican officials said hospitals were seeing fewer new cases of people with symptoms from the new swine flu virus and cut the estimated death toll from the outbreak.
"It would still be imprudent to say that we're past the worst of it but I do think ... we are in a stage of stabilization," Mexican Health Minister Jose Angel Cordova told reporters.
Costa Rica, Italy, and Ireland confirmed cases of the virus, which has now been found in 18 countries.
In Geneva, the World Health Organization said H1N1 influenza had not spread in a sustained way outside North America, as would be required before the pandemic alert level is raised to its highest level. But it said that would probably happen soon.
"I would still propose that a pandemic is imminent because we are seeing the disease spread," Michael Ryan, WHO director of Global Alert and Response, told a briefing.
Few are ready to take chances with the new virus, widely dubbed swine flu.
In Hong Kong, police quarantined a hotel after a Mexican guest fell ill with the virus, which may have killed more than 100 people in Mexico, the worst-hit country. Mexico called the action "unjustified" and advised its citizens to avoid travel to China.
Mexican authorities cut their suspected death toll to up to 101 from as many as 176 as more test samples came back negative. Fewer patients with severe flu symptoms were checking into hospitals, suggesting a falling infection rate, and no new deaths were reported in Mexico City in the past two days.
The World Health Organization said 15 countries had reported 615 infections, not including the later reports of confirmed cases in Ireland, Italy and Costa Rica.
The United States, the second hardest-hit country, said it had confirmed 160 cases in 21 states.
U.S. officials said they were encouraged by reports from Mexico that the outbreak may be leveling off, although they said it was too early to relax.
"We are remaining vigilant," said Dr. Anne Schuchat of the U.S. Centers for Disease Control and Prevention. "We have seen times where things appear to be getting better and then get worse again. ... I think in Mexico we may be holding our breath for some time."
Almost all infections outside Mexico have been mild. The only death in another country has been a Mexican toddler who was taken to the United States before he fell sick.
President Barack Obama said the United States was responding aggressively to the new flu strain and was closing some schools temporarily and distributing antiviral drug supplies as needed.
The White House said Obama spoke to Mexican President Felipe Calderon on Saturday about U.S.-Mexican cooperation on limiting the spread of the virus.
Scientists are still trying to assess how the new virus behaves and how it compares to regular seasonal flu strains, which kill between 250,000 and 500,000 globally every year.
The outbreak remains tiny compared with other epidemics such as malaria, hepatitis and meningitis. But the WHO hiked its pandemic alert level to 5 from 3 this week -- the last step before a pandemic -- due to its rapid spread and the possibility it could hit hard in poor and disease-prone communities, including among people with HIV.
Ryan said the WHO would send more than 2 million treatment courses of antiviral drugs to poor countries to help them prepare for the virus, which is already causing havoc with a travel industry that flies hundreds of thousands of people to and from Mexico each week.
China suspended flights to Mexico after Hong Kong authorities on Friday confirmed a Mexican man who flew via the Chinese mainland was infected with the flu strain. Hong Kong was hit hard by the 2003 SARS outbreak.
Police in surgical masks quarantined 200 guests and 100 staff inside a Hong Kong hotel where the Mexican, 25, had been staying, saying they would be confined for a week.
"They said everybody needed to go back to their rooms. I don't want to go to my room because I want to be out," an Australian man at the hotel told a TV reporter by telephone.
Public hospitals in Mexico have noted a steady drop in patients turning up with fevers, suggesting the infection rate may be declining as people don face masks and use hand gel.
Cordova said of 159 suspected flu deaths, tests showed 58 died of other causes. He said 16 deaths were confirmed as caused by the H1N1 flu and 85 were being tested.
In Mexico City, big parks, museums and zoos were shut and in the sprawling metropolis of 20 million people many were heeding a government call to stay home for a prolonged five day-holiday to try to stem new infections.
Jose Francisco Suarez, 15, said he wanted to get back to school. "We're sick of this situation. A few days off school wouldn't be so bad but now there's nothing to do," he said during a break playing basketball with two friends.
(Additional reporting by reporting by Cyntia Barrera, Louis Egan, Alistair Bell and Kieran Murray in Mexico City Anahi Rama and Tan Ee Lyn in Hong Kong, Laura MacInnis in Geneva, Silvia Aloisi in Rome; Writing by Andrew Quinn; Editing by Alan Elsner and Peter Cooney)