A top federal health official said the government's concern over the swine flu outbreaks in the United States and Mexico has grown since Thursday -- and a handful of influenza experts worry the deadly, never-before-seen hybrid strain may spur a pandemic.
Dr. Richard Besser, acting director of the U.S. Centers for Disease Control and Prevention, said that health officials confirmed yet another U.S. case of swine flu in California today, bringing the total number of Americans infected with the disease to eight.
Though it is still too early to say for certain whether a swine flu pandemic is possible or likely, the cases, all of which have occurred in California and Texas, have aroused concerns among the public, Besser acknowledged.
"We are worried as well," he said. "Our concern has grown since yesterday in light of what we've come to know since then."
Thus far, the first seven Americans found to have contracted the new variant have recovered, which Thursday led health officials to urge calm while the investigation into the virus continued.
Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases, had said during a Thursday afternoon press conference that the strain did not "[look] like a very severe influenza. ... We don't think this is time for major concern around the country."
The sentiments were echoed by Canada's Dr. Michael Gardam, director of infectious disease prevention and control at Ontario's public health agency, in a Thursday night interview with the Canadian Broadcasting Corporation. Moreover, the World Health Organization has not yet made a change to the pandemic threat level -- the established worldwide barometer for pandemic threat.
Still, Mexican officials reported that what is believed to be the same mutant strain of swine flu already has killed at least 16 people in Mexico, and possibly as many as 61.
John Barry, author of "The Great Influenza," said he believes there is a chance that the infections signal the beginning of the next pandemic -- a global disease outbreak that occurs when a new virus emerges for which there is little or no immunity in the human population, begins to cause serious illness and then spreads easily person-to-person worldwide.
"Obviously, this is an extremely serious situation," he said, adding that the real determinant as to how dangerous this virus will become lies in how easily it is spread from person to person.
"If the virus is halfway efficient at that transmission, we have the next pandemic," he said. "No way it can be contained in a place like Mexico City, and it's already in California, and probably some places -- if not every place -- in between."
Barry is not the only one to harbor such concerns.
"If 16 to 60 out of about 800 cases in Mexico have died, then this is indeed a serious public health threat deserving of the full attention of the U.S. public health infrastructure," said Robert Garry, a microbiologist at Tulane University.
And Dr. Martin Blaser, chairman of the Department of Medicine at New York University Langone Medical Center, agreed the situation is serious.
"This is worrisome, because it is a swine, avian, human recombinant; it involves people who do not have any obvious exposure to swine," he said.
He further noted that the patterns of spread so far point toward the possibility that the virus may have been spread through human-to-human contact.