US Agricultural Secretary Tom Vilsack said Tuesday that the virus should not be called "swine flu" because there is no indication that any swine from the United States has been infected.

"This really isn't swine flu." Secretary Vilsack said. "It's H1N1 virus. That's very, very important. And it is significant, because there are a lot of hardworking families whose livelihood depends on us conveying this message of safety.

"I want to reiterate that US pork is safe," Secretary Vilsack said. "While we in the United States are continuing to monitor for new cases of H1N1 flu, the American food supply is safe."

"What we call this flu is important," said Chris Novak, chief executive officer of the National Pork Board. "Consumers and our international customers need to be assured that pork is safe and will continue to be safe to consume. Calling this swine flu has the potential to cause confusion. There simply is no reason for anyone to be concerned about the safety of eating pork."

Earlier, the World Organization for Animal Health, also known as the OIE, had recommended renaming the current influenza because it contains avian and human components and because no pig has been found to be ill. The OIE, which manages the fight against animal diseases globally, compared its preference for a geographic naming of this influenza to the Spanish influenza, a human flu pandemic with animal origin that killed more than 50 million people in 1918-1919. The current flu has not reached pandemic proportions according to the World Health Organization.

"The virus has not been isolated in animals to date. Therefore, it is not justified to name this disease swine influenza," the Paris-based organization said in a statement.

According to Peter Cowen, associate professor of epidemiology and public health at North Carolina State University, the H1N1 virus is being called "swine flu" because of the 1918 outbreak in Spain. That virus, Cowen said, became known as the swine influenza virus because it caused significant mortality in both swine and human populations.

Professor Cowen, as did the OIE, notes that it appears that people who have come down with the current novel H1N1 virus have had no contact with swine. The reason this virus is being called swine flu, Professor Cowen said, "is the history and evolution of the virus. It also rests on the fact the some of the genetic analysis indicates that elements from viruses that have traditionally been found in swine populations are incorporated.

"However, since we know nothing of how this virus has gotten into the human population and there apparently is no history of swine exposure, it probably makes more sense epidemiologically to refer this simply as an H1N1 virus."

Professor Cowen noted that the H5N1 virus prevalent in Asia was known as avian influenza or bird flu, but that it, over time, is becoming known by its viral strain, rather than bird flu.

As for the widespread public use of the term swine flu, Professor Cowen said it's unfortunate because the name implies a simple, zoonotic transmission between swine and people, when in reality, its origin and epidemiology is likely to be much more complex.