The escalation in the swine flu situation on Saturday underscored concerns by international, federal and local health agencies over the threat of the new virus, even as government health officials said much remains unknown.
But if one thing is clear about the spread of this virus, it is that containment is no longer an option.
Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases said broad spectrum of the illness is expected in the United States.
"It's clear that this is widespread," said Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases, at a press conference Saturday afternoon.
"We do not think that we can contain the spread of this virus," Schuchat added. "Having found virus where we have found it, we are very likely to find it in other places. ... We are not at a point where we can keep this virus in just one place."
The cases further demonstrate that health officials do not know where else the virus might turn up. Details of swine flu's spread in Mexico also remain murky. A team sent by the Centers for Disease Control and Prevention is now on the ground there seeking clues on the origin and spread of the disease.
"What we still don't know is how widespread it is," said Schaffner. "The question is: How long have things been going on in Mexico, and how attentive have they been in terms of what's going on in their country?"
Schaffner added that had it not been for the death cases in Mexico, the swine flu would have largely gone unnoticed in the United States.
"My observation has been, were it not for the problem in Mexico, this would have been on page 15 instead of page 1," he said. "Because each year we have dominant influenza strains but we also have occasional strains that don't fit the dominant patterns."
ABC News' Matt Hosford contributed to this report.