The swine flu epidemic spread deeper into the United States, Europe and Latin America -- and in Canada, back to pigs -- even as Mexico's health chief hinted Sunday it may soon be time to reopen businesses and schools in the nation where the outbreak likely began.

The virus spread to Colombia in the first confirmed case in South America, worrisome because flu season is about to begin in the Southern Hemisphere. More cases were confirmed in Europe and North America; the World Health Organization said at least 787 people have been sickened worldwide.

Dr. Richard Besser, acting chief of the US Centers for Disease Control and Prevention, said swine flu is spreading just as easily as regular winter flu, with 226 confirmed cases in 30 US states.

"The good news is when we look at this virus right now, we're not seeing some of the things in the virus that have been associated in the past with more severe flu," Besser said. "That's encouraging, but it doesn't mean we're out of the woods yet."

Mexican Health Secretary Jose Angel Cordova said the virus that has killed 19 people in Mexico and sickened at least 506 apparently peaked here between April 23 and April 28. A drastic nationwide shutdown appears to have helped prevent the outbreak from becoming more serious, he said.

"The evolution of the epidemic is now in its declining phase," Cordova declared.

He said officials would decide Monday whether to extend the shutdown or allow schools and businesses to reopen on Wednesday.

Pablo Kuri, an epidemiologist advising Cordova, said on Sunday that tests have confirmed a swine flu death in Mexico City on April 11, two days earlier than what had been believed to be the first death.

He also said there have been no deaths among health care workers treating swine flu patients in Mexico, an indication that the virus may not be as contagious or virulent as initially feared.

The closed events made for a surreal Sunday in Mexico, as parishioners celebrated Mass via television, camera operators were the only ones in stadium bleachers and parks, museums, restaurants, theaters and other attractions were closed.

Sunday also marked the official start of campaigning for July 5 congressional elections -- but all public campaigning was banned to prevent gatherings where the virus could spread.

Gabriela Cuevas Barron of the conservative National Action Party, giddily claimed she was launching Mexico's first virtual campaign, promising in a Webcast to work for a cleaner and safer Mexico City -- for now, through Twitter, Facebook and Youtube. Meanwhile, the leftist Democratic Revolution Party was already up with a Facebook page for its candidates.

In the Canadian province of Alberta, officials quarantined about 220 pigs that became infected from a worker who had recently returned from Mexico. It was the first documented case of the H1N1 virus being passed from a human to another species. Canada stressed that pigs often get the flu and there's no danger in eating pork.

Egypt has ordered all pigs in the country slaughtered as a precaution, sparking riots Sunday by pig farmers who threw stones at police.

Health officials around the world cautioned that despite encouraging signs, swine flu still poses a very real threat.

"Most experts would agree that the current outbreak that we are experiencing is mild to moderate in severity," Dr. Jon Andrus of the Pan American Health Organization said in a teleconference from Washington. "That is not to say that things cannot change very rapidly and very dramatically."

Under one scenario, the virus could peter out now, only to roar back in the fall when flu seasons begins. That's why health officials are watching the Southern Hemisphere so closely.

"Certainly, maybe, this current round of activity has peaked, but we are only 10 days into this outbreak," WHO spokesman Gregory Hartl told reporters in Switzerland. "I think we would want to wait a while before making a definitive decision."

Editor: Yan