The head of the Centers for Disease Control and Prevention warned Monday that bird flu in Asia is highly likely to mutate into a virus transmittable from person to person, raising the prospect of a global epidemic.

Such a pandemic could occur next year, said Dr. Julie Gerberding, head of the federal agency, which has organized a special team to monitor the disease.

Gerberding noted that the characteristics of this flu are similar to ones that have caused major epidemics in the last century, including the 1918 Spanish flu, which killed millions.

“The reason this is so ominous is because of the evolution of flu,” she said. “You may see the emergence of a new strain to which the human population has no immunity.”

The flu has swept through birds in parts of Asia, with a number of deaths reported among people who caught the disease from chickens or ducks. The mortality rate is very high-about 72 percent of identified patients, Gerberding said.

There also have been documented cases of this strain of flu being transferred from person to person, but the outbreak was not sustained, she said.

“We are expecting more human cases over the next few weeks because this is high season for avian influenza in that part of the world,” said Gerberding. Although cases of human-to-human transmission have been rare, “our assessment is that this is a very high threat.”

The U.S. government has ordered 2 million doses of vaccine against the bird flu. This should give manufacturers a head start on making the shots to combat a full-blown epidemic of an H1-type of flu in this country.

The CDC assessment is based on the known history of the flu virus, Gerberding said in remarks at the national meeting of the American Association for the Advancement of Science.

The avian flu now spreading in Asia is part of what is called the H1 family of flu viruses. It is a pathogen that is notorious in human history.

“Each time we see a new H1 antigen emerge, we experience a pandemic of influenza,” said Gerberding.

In 1918, H1 appeared and millions died worldwide. In 1957, the Asian flu was an H2, and the Hong Kong flu in 1968 was an H3.

There had been small appearances of H1 avian viruses in other years, but nothing like the H5 now rampaging through the birds of Asia.

“We are seeing a highly pathogenic strain of influenza virus emerge to an extraordinary proportion across the entire western component of Asia,” Gerberding said.

A study found the virus can infect cats that then can transmit the disease to other cats, which Gerberding said was “another harbinger” of the possibility of a human pandemic.

“The science here is all alerting us that we have a great deal to be concerned about,” she said.

A special flu team, organized last year at the Centers for Disease Control and Prevention, monitors the spread of the avian flu and analyzes the strains as they appear.

The agency is also plugged into an international monitoring system that should provide an early warning of the emergence of a deadly new flu.