Mexican officials announced today they would allow most nonessential businesses to reopen Wednesday, after it ordered them closed Friday after the deadly outbreak of the swine flu virus.
On Sunday, Mexico's health ministry said that the worst of the outbreak had passed, partially because of the shutdowns , and that the virus might turn out to be no worse than a typical seasonal flu outbreak.
"The virus has entered into a stabilization phase. The cases are starting to decrease," President Felipe Calderon said, predicting that Mexico would soon begin to get back on its feet.
Meanwhile in the United States, St. Francis Preparatory School in New York City -- considered last week as the epicenter of the country's swine flu infections, has been scrubbed down and will reopen today for the first time since the virus was identified.
As students return to the school, many packing bottles of hand sanitzers in their backpacks, medical experts are concluding that the swine flu infection may not be any more dangerous than a normal outbreak of flu.
But the country's medical authorities aren't ready to ease restrictions, and more than 333,000 students are out of class today as schools across the country are taking no chances and have shut down.
In fact, two more New York schools closed their doors starting today, including one in Syracuse and another on Long Island.
In addition, hospital emergency rooms continue to fill up with patients who have "swine flu jitters," hand sanitizers are disappearing from drug store shelves and airlines are taking unusual precautions. British Airways is handing out masks to Mexico-bound passengers. Lufthansa is putting a doctor on flights to Mexico. And Alaska Airways is eliminating pillows, hoping that will help halt the spread of germs.
The jitters persist despite efforts to tamp down fears about the potency of the H1N1 virus that has been dubbed swine flu.
The Centers for Disease Control and Prevention has analyzed the genetics of the virus and noted that there have been relatively few "severe" cases of illness.
"We are seeing encouraging signs that the virus so far is not looking more severe than a strain we would see during seasonal flu," concluded CDC Acting Director Dr. Richard Besser.
Nevertheless, the CDC officially confirmed 279 cases in 36 states Monday.
And there is one worrisome pattern. While most flus strike the very young and the elderly, this virus has taken its toll on older children and younger adults. Of the 30 people hospitalized in the U.S. with swine flu, many fit this category. And nine of the 19 deaths in Mexico attributed to swine flu were people between the ages of 21 and 39.
In Mexico, where the virus outbreak has been most virulent, the country will decide today whether to reopen schools and businesses shut down last week in an effort to contain the spread of swine flu.
In an interview with state television broadcast Sunday night, Mexico President Felipe Calderon defended the nationwide shutdown, saying, "We have succeeded in detaining or at least slowing the spread of the virus precisely because the measures have been the correct ones."
Mexico's Health Minister Jose Angel Cordova said at a news conference that the lockdown would "not happen just like that," adding, "There will have to be training, preparations for teachers and parents."
As Mexican authorities ponder when and how to reopen businesses and schools, the virus spread to Colombia in the first confirmed case in South America, a fact which has worried health officials since the flu season is about to begin in the continent.
Mexico also found itself embroiled in a row with the Chinese government over its decision to quarantine more than 70 Mexican travelers in the country. Mexico's ambassador to China, Jorge Guajardo, told reporters that even the Mexican consul in Guangzhou was held briefly after returning from a trip to Cambodia.
Calderon described such measures as "unfair," adding, "because we have been honest and transparent with the world some countries and places are taking repressive and discriminatory measures because of ignorance and disinformation."
He did not mention China by name but Mexico's Foreign Relations Department released a statement later, saying that Mexico would send a jet to several Chinese cities "where Mexicans have expressed their intention to return to Mexico."
China's Foreign Ministry denied it was discriminating against Mexicans.
Swine Flu Cases Continue to Increase; WHO Urges Alertness
By Monday morning, the World Health Organization had confirmed 1,085 cases in 21 countries -- up from Sunday's totals of 787 people in 17 countries.
Mexico's Cordova said there have been at least 568 confirmed cases of the disease and raised the death toll in that country, believed to be the epicenter of the outbreak, to at least 22. In the U.S., the virus claimed the life of a toddler in Texas last month.
WHO epidemic and pandemic diseases spokesman Gregory Hartl said Sunday that though the current epidemiology in Mexico might show a slowdown, history must be considered when evaluating the virus' potential to come back.
"I also would like to remind people that in 1918, the Spanish flu showed a surge in the spring and then disappeared in the summer months only to return in the autumn of 1918 with a vengeance, and we know that killed eventually 40 to 50 million people," Hartl said. "So I think while tracing these kind of curves of activity -- increasing, decreasing activity -- we cannot lower our guard."
As for the CDC's analysis of the H1N1 virus, Besser said, "what we've found is that we're not seeing the factors that were associated with the 1918 pandemic, we're not seeing the factors that are, were associated with other H1N1 viruses, and that's encouraging."
But though officials are cautiously optimistic, whether the virus will reemerge when the typical flu season starts in the fall is still unclear.
"Every virus is new," Besser cautioned. "And what it will do is different. And so you're hitting a critical point: What will happen this spring and summer?"
He reiterated that the virus is spreading "quite easily," and that he expects to see reports of more confirmed cases in this country.
Pandemic Alert Level Depends on H1N1 Virus Spread
The WHO's current pandemic alert level stands at phase five, which "is a strong signal that a pandemic is imminent," according to the organization's guidelines.
Hartl added Sunday that a time frame for an upgrade in alert level "is not very easy to predict, because transmission of influenza virus, or of any virus for that matter, does not necessarily always move at the same speed. There could be hiatus in its spread, especially [because] we have not seen any confirmed instances of sustained human-to-human transmission in communities outside of the Americas."
"We don't know when that will happen; certainly we remain on alert in case that happens," he said. "But ... it would not be prudent to try to make a prediction" on the timing of a potential decision to step up the alert level.
The next level, six, would indicate that "a global pandemic is under way," the guidelines say.
Swine Flu Concerns: Safe to Eat Pork?
There have been concerns about the safety of eating pork since the outbreak of the virus, though officials have maintained that the meat is safe. Global health officials have ceased calling it swine flu in favor of its scientific designation, H1N1, as part of the effort to reinforce that notion.
But on Saturday, concerns grew after Canadian officials confirmed that pigs on a farm in that country tested positive for the virus. The farm has been placed under quarantine.
WHO food safety scientist Dr. Peter Ben Embarek said today that a farm worker who had recently visited Mexico likely brought the virus to the farm, but that the humans and animals infected in that case are recovering.
Embarek said the virus infected only about 10 percent of the herd of 2,200 pigs.
"This tells us that, also for the animal population, it doesn't seem to be a very serious disease," Embarek said. "And it's apparently, from what we know, something that is not surprising and could be expected from a virus like this."
He added that, though farm workers and those who slaughter and process infected animals could be at a greater risk for picking up the disease, "from the consumer point of view, there is absolutely no risk of consuming cooked products," and that the meat trade should not be restricted.
Obama: U.S. Acting 'Quickly and Aggressively' to Combat H1N1
President Obama said in his weekly address to the nation Saturday that the United States is acting "quickly and aggressively" to prepare for a potential pandemic, and is "investing in every resource necessary to treat this virus and prevent a wider outbreak."
His newly-confirmed secretary of health and human services, Kathleen Sebelius, said on "This Week" that the government is taking action to develop a vaccine for the H1N1 virus in addition to preparing for the fall flu season.
"The good news is we're in the right seasonal time. We can accelerate the seasonal flu vaccine which we're doing right now, to be prepared and ready for what we know will hit this fall and winter," Sebelius said, "At the same time, we are in the stages of growing the virus, testing it, and we can be ready to do both simultaneously."
Obama added the nation's stockpile of antiviral medications has been opened up to the states, with a quarter of the supply of 50 million courses of treatment already released. The U.S. government also purchased 13 million treatments to replenish the stockpile, he said.
The WHO said Saturday that it released 2.4 million antiviral courses to 72 developing countries, including Mexico.
Obama added that "out of an abundance of caution," he has asked Congress for $1.5 billion to be set aside for more medicines, supplies and the development of an H1N1 flu vaccine.
Officials continue to caution those who feel ill to stay home, for individuals to wash their hands frequently and for schools with a confirmed case of the virus to close for up to 14 days, with frequent reevaluation of their particular situation.
Schools are of particular concern, the CDC's Dr. Anne Schuchat said Saturday, because children take longer to shed viruses and other diseases, and often do so without symptoms. The majority of the swine flu cases in the United States have occurred in people younger than 20 years old. The median age of those with the disease is 17, though the ages range from 1 to 81, according to Schuchat.
"The goal" of social distancing efforts like school closures, Schuchat said, "is to try to decrease the ongoing numbers of cases and to shift them to a later time by slowing transmission."
Religious organizations altered their weekend services to reduce close contact between congregants. Some made the decision not to place communion wafers into individuals' mouths or to serve wine, an attempt to limit the risk for transmission of the disease.
ABC News' Gregory Croft, Ayana Harry and wire reports contributed to this report.