From combined dispatches
Avian flu poses the single biggest health threat to the world and officials might not have all the tools they need to fight it, the head of the Centers for Disease Control and Prevention said yesterday.
Dr. Julie Gerberding said the expected mutation of a flu virus that has swept through chickens and other poultry in Asia has the potential to become as deadly and infectious as viruses that killed millions of people during three influenza pandemics of the 20th century.
“This is a very ominous situation for the globe,” Dr. Gerberding told a meeting of the American Association for the Advancement of Science, calling it the “most important threat that we are facing right now.”
“I think we can all recognize a similar pattern probably occurred prior to 1918,” she said, referring to the 1918 pandemic of influenza, which also passed from birds to people and killed between 20 million and 40 million people globally.
The genes of the avian flu change rapidly, she said, and researchers think it is likely that the virus will evolve into a pathogen deadly for humans.
In Asia, several deaths have been reported among people who caught the flu from chickens or ducks. The mortality rate is high ” about 72 percent of identified patients, Dr. 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.
Dr. Gerberding said influenza was far more infectious than severe acute respiratory syndrome, or SARS, which swept out of China in 2003, killing 800 people and causing global concern before it was stopped.
Health specialists also have pointed out that influenza kills much faster than diseases such as AIDS, taking tens of millions of lives in the space of weeks or months.
“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,” Dr. Gerberding said. Although cases of human-to-human transmission have been rare, “our assessment is that this is a very high threat.”
Dr. Gerberding said the assessment is based on the known history of the flu virus, and that her agency is getting ready for a pandemic next year.
The avian flu 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,” Dr. Gerberding said.
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.
The CDC last year organized a special flu team to monitor the spread of the avian flu and to analyze the strains as they appear. The U.S. government has ordered 2 million doses of vaccine that would protect against the known strains of avian flu.
Dr. Gerberding said this would give manufacturers a head start on making the shots that would be needed to combat a full-blown epidemic of an H1-type of flu in this country.
“We are seeing a highly pathogenic strain of influenza virus emerge to an extraordinary proportion across the entire western component of Asia,” she said. “The reason this is so ominous is because of the evolution of flu. … You may see the emergence of a new strain to which the human population has no immunity.”
Research has shown that the virus can infect cats who can then infect other cats, which Dr. Gerberding said was “another harbinger” of a human pandemic.
“The science here is all alerting us that we have a great deal to be concerned about,” she said.
The CDC is plugged into an international communication and monitoring system that, it is hoped, will give an early warning of the emergence of a deadly new flu.
At the same time, the agency is helping to produce the 180 million or so doses of vaccine for regular flu that are needed annually. Dr. Gerberding said the timeline for producing the regular vaccine yearly is tight, with little room for problems. To produce a vaccine in response to the sudden emergence of an H1 flu bug would require an extraordinary effort, she said.
“We don’t now have the capacity to do both,” she said.
“There is no wiggle room here,” she said. Making an avian flu vaccine in case of an outbreak would be faster than starting from scratch, “but we just don’t have the surge capacity to produce both.”
So avian flu vaccine would be rationed.
People transmit the flu virus before they show symptoms of illness, so it would be almost impossible to stop its spread by watching or isolating sick people, Dr. Gerberding said.
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