Outside Mexico, where 159 people have died, the United States has been the country worse hit by the swine flu outbreak. Many of the cases appear to be students who recently visited Mexico.
Addressing the National Academy of Sciences Monday, President Obama acknowledged the efforts to keep pace with the spread of the disease within the United States.
"We are closely monitoring the emerging cases of swine flu in the United States," he said. "And this is obviously a cause for concern and requires a heightened state of alert. But it is not a cause for alarm."
There is no vaccination for the swine flu strain, which has elements of pig, bird and human strains. But officials said they have ramped up medical surveillance around the country and, as part of the emergency declaration, freed up state and federal resources for prevention. Officials also emphasized the importance of individual care and good hygienic practices.
"Even if this outbreak is a small one, we can't anticipate we won't have follow-up outbreaks," U.S. Homeland Security Secretary Janet Napolitano said.
A different scenario is unfolding across the border in Mexico. While authorities hunt for the source of the swine flu outbreak, the country is under lock down. Schools, museums, parks and even churches in Mexico City have been shut down by the government. A leading business group estimates that canceled events and closure of establishments to prevent the spread of swine flu is costing Mexico City at least $57 million a day.
All of Mexico's Mayan ruins and Aztec pyramids have also been shut down until further notice.
"I haven't been out for days," said one woman, who only left to bring her baby to the doctor for a routine vaccination.
The government has advised people to stay home and indicated that those infected by the virus could be isolated. In the country's deserted capital, public events were cancelled for the next week or so. Sales of masks have soared as people try to prevent themselves from the potentially deadly disease.
Mexican officials are hoping the 10-day shut-down will be enough to cover the two-day incubation period and the seven-day recovery of anyone who has the virus. On Wednesday, however, the Associated Press reported that Mexico City Mayor Marcelo Ebrard said the swine flu situation in the city seems to be stabilizing, with only one more death since he last spoke. The AP further reported the mayor as saying that if the death toll continues to taper off, he will consider easing the shutdown of the city.
Mexico's first suspected case of the swine flu was detected in the remote farming village of La Gloria, where 5-year-old Edgar Hernandez contracted the disease nearly one month ago, authorities say.
"The most likely way that this young boy got the infection was from another person who had been in contact with the pigs," said Dr. Kathryn Edwards of Vanderbilt Medical Center.
More than 800 people in the town of 2,000 were infected, authorities say, but no deaths were reported. It took seven days for Mexico to confirm its first cases of swine flu, according to World Health Organization estimates.
Officials say it's still too early to determine how the disease spread from La Gloria into a global health emergency.