By David Brown
Washington Post Staff Writer
Friday, June 12, 2009
The World Health Organization yesterday declared the seven-week-old outbreak of the novel H1N1 influenza virus a pandemic, marking it as a historic global health event, one whose consequences may not be known for years.
The announcement -- expected for weeks but made with some reluctance -- essentially warns the WHO's 194 member nations to get ready for the new flu strain, which is likely to infect as much as one-third of the population in the first wave and return in later waves that may be more severe.
"The world is moving into the early days of its first influenza pandemic of the 21st century," Margaret Chan, the WHO's director general, said at an afternoon news conference in Geneva. "We anticipate this action will raise many questions and that often these questions do not have simple answers."
Simultaneously, Chan said the WHO is advising the world's makers of flu vaccines "quickly to prepare commercial-scale pandemic vaccine of this H1N1 virus," which was called swine flu at first because it is thought to have emerged in pigs.
The world suffered three influenza pandemics in the 20th century: the "Spanish" flu of 1918-1919, which killed at least 50 million people; and the far less severe "Asian" flu of 1957 and "Hong Kong" flu of 1968.
The move to Phase 6, the highest level in the WHO's graduated scale of pandemic alerts, means the virus is being passed freely between people without easily traced chains of infection -- a state known as "community level transmission" -- in two or more regions of the world.
In the United States, where the new strain is circulating in all 50 states, the WHO's decision "makes no practical difference for state and local governments," said Thomas R. Frieden, the newly appointed director of the Centers for Disease Control and Prevention.
The virus came to world's attention on April 21, when the CDC announced it had learned of two cases of a previously unknown strain of swine flu in Southern California. Three days later, Mexico announced it had hundreds of cases and 68 deaths. To date, there have been more than 13,000 confirmed U.S. cases -- about 1,000 requiring hospitalization -- and 27 deaths.
Worldwide, 28,774 cases in 74 countries, and 144 deaths, had been reported as of yesterday.
The virus is less lethal than most experts expected the next pandemic strain to be, and the WHO has been reluctant to declare Phase 6 for fear of confusing governments and causing needless anxiety. However, large outbreaks in Australia, Chile and Japan, as well as suspicions that the virus is far more widespread in Europe than officials there have admitted, made the move inevitable.
"I think it was the right call," said Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, who has urged pandemic preparedness over the last five years. "We are all sitting here with bated breath, waiting to see what is going to happen in the next six to 12 months."
The dean of U.S. influenza researchers, Edwin D. Kilbourne, 88, agreed. "Even if it errs on the side of being a little bit excessive, the warning should go out that things could get worse," he said.
Chan said that in the Southern Hemisphere, which is entering winter flu season, the new H1N1 strain "is actually crowding out the seasonal influenza virus -- this is a very typical feature of previous pandemics."
The declaration of Phase 6 does not by itself initiate any particular action, nor does it predict the pandemic's ultimate severity, which is likely to vary between regions, ages, ethnic groups and economic strata.
"Most important, we do not know how this virus will behave in conditions typically found in the developing world," Chan said.
The WHO is not recommending that countries limit travel or commerce -- two strategies mentioned when many experts thought the next pandemic might be caused by the H5N1 "bird flu" strain, which has infected 433 people and killed 262, mostly in Southeast Asia, since 2003.
Chan said a single set of recommendations for all countries "clearly is not appropriate." However, the declaration should give them "the space and the capability to recalibrate response."
The biggest immediate questions are when a vaccine against the virus will be available, how many doses will be made and who will get it. In theory, the first doses could be ready by September, and manufacturers might be able to make 2 billion doses over the next year. But industrialized countries have contracts to buy nearly all the production.
Securing vaccine for poor countries, where Chan says she expects the virus to sketch a "bleaker" picture than it has so far, will be one of her chief tasks.
Although the full personality of the new virus is still emerging, it appears to preferentially infect children and young adults. In the United States, 57 percent of confirmed cases are in people 5 to 24 years of age, a CDC official said yesterday.
In contrast with seasonal flu, few severe cases have been seen in people older than 60. As with many flu strains, however, pregnant women and people with chronic illnesses such as asthma, heart disease, diabetes and emphysema are at higher risk for severe illness and death.
The WHO is describing this as a "moderate" pandemic, eschewing the word "mild" it had previously used to describe the illness.
Many experts think the declaration is a month overdue.
Many European countries are testing for the H1N1 virus only in people who have traveled recently to the Americas or had contact with a traveler or a confirmed case. A 40-year-old Spanish pediatrician told The Washington Post that soon after the American outbreak began, rapid-test kits for influenza A -- an initial screening tool for finding the new virus -- were removed from the hospital in the Madrid suburbs where he works. Patients who met the "epidemiological criteria" were referred to a central location for testing.
The net effect was to reduce the chance of finding cases in people without travel histories and to prevent early discovery of "community transmission" of the virus.
The reason for this strategy is uncertain, but some observers think that no country wanted to be seen as responsible for triggering the Phase 6 declaration. Chan yesterday named no country's outbreak as the reason for the WHO's decision.