Julie Gerberding

A top U.S. health official says the country is preparing for the possibility of a deadly global pandemic of avian flu. The head of America's disease-tracking agency, the Centers for Disease Control, says avian flu poses an ominous threat to the world.

As the season for avian flu begins in Asia, the message Centers for Disease Control chief Julie Gerberding has brought to Washington this week is that her agency is very concerned about the virus.

She told the American Association for the Advancement of Science convention Monday that the ailment is the biggest disease threat to the world. She said a highly infectious strain is circulating in chickens and ducks in Asia and could mix with human strains. The virus can jump directly from birds to people or can be transmitted through pigs.

On Tuesday at the National Press Club in Washington, Dr. Gerberding told journalists that her agency is taking precautionary measures to prevent a new strain from spreading in Asia and abroad.

"There are more pigs, people, and poultry in that environment than we have ever seen before,” she noted.  “That is the formula for emergence of new flu strains.  We already know this particular strain of virus can infect people, we already know that it can occasionally move from person to person, and we know how these viruses evolve. So it is a worrisome situation and we are taking many steps to be as prepared as we can and to prevent the transmission of a new virus strain in the global arena."

The avian flu has a high mortality rate. About 72 percent of those infected die from it. It emerged in Hong Kong in 1997 and there is no immunity to it.

Dr. Gerberding says her agency is working with the World Health Organization (WHO) and national health ministries in Asia to expand the ability to detect the emergence and spread of a new avian flu strain. She says the United States is preparing to have a sufficient stockpile of antiviral drugs to ship to any region where the disease is found and has ordered two million doses of a vaccine that would protect Americans against known avian flu strains.

The U.S. health official says she does not mean to imply an avian flu pandemic is imminent. She says it takes time to evolve and circulate.  Such a situation occurred in 1918, when flu also passed from birds to people.  However, it eventually killed more than 25 million people worldwide.

"When avian virus evolved to form the 1918 flu strain that caused the global pandemic, It didn't happen overnight,” she added.  “It happens in a series of progressive steps where you'll see local outbreaks and the virus gradually evolves to become more efficiently transmitted from person to person. That's why the efforts that we're making to scale up and speed up the laboratory detection capabilities around the globe are so critically important to our effort."

Dr. Gerberding says the world needs to be shaken out of its complacency concerning avian flu virus.