• Jon is a contributing correspondent for Science.

On the Precipice of Pandemic

29 April 2009 7:33 pm

The World Health Organization has raised the threat of the current outbreak of swine flu from phase 4 to 5, officials announced this evening in Geneva. Phase 6 is a full-scale pandemic. “Influenza pandemics must be taken seriously precisely because of their capacity to spread rapidly to every country in the world,” said Margaret Chan, WHO’s director-general, at a press conference.

As Chan and other officials explained, WHO made the decision to move from phase 4 to 5 because of evidence that the virus had spread from humans to humans in both Mexico and the United States, two countries in the same region. “All countries should immediately now activate their pandemic preparedness plans,” said Chan. “Countries should remain on high alert for unusual outbreaks of influenza-like illness and severe pneumonia.”

If human-to-human transmission is confirmed in another region—which now seems likely—WHO will raise the threat level to phase 6.

Chan explained that she has been in touch with leaders from several countries, the pharmaceutical industry, and the head of the World Bank to discuss appropriate health measures, potentially ramping up production of antivirals and a vaccine, and finding money to help developing countries combat their outbreaks. The change to a phase 5 alert, she said, should signal that “certain actions now should be taken with increased urgency and accelerated pace.”

As severe cases of disease still have not been seen outside of Mexico and the United States, Chan says it’s still unclear just how aggressively countries should respond. But she said countries should step up surveillance and consider measures such as closing schools and delaying public meetings to stem local outbreaks.

Chan stressed that “not every country has the same level of preparedness and sophistication,” and she urged the world to pay close attention to developing countries. “The international community should treat this as a window of opportunity to ramp up preparedness and response,” said Chan. “It really is all of humanity that is under threat during a pandemic. We do not have all the answers right now, but we will get them.”

The labels matter, but ultimately, "what we do means a lot more than what it is called," said Richard Besser, acting director of the U.S. Centers of Disease Control and Prevention, yesterday in response to a question about WHO's earlier decision to move to phase 4. "And what we're doing is being very aggressive, looking at what's going on at the community level and adjusting and adapting our guidance and our actions based on what's taking place on the ground.”

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