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  • Jon is a contributing correspondent for Science.
 

Pandemic Definition Continues to Mystify

26 May 2009 4:26 pm
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As cases of swine flu continue to increase in several countries, the World Health Organization (WHO) maintains that the outbreak does not merit the label "pandemic." And in the United States, which accounts for just over half of the 12,954 confirmed cases of the disease reported to WHO from 46 countries, signs indicate the outbreak may have peaked.

Case counts in part reflect the intensity of a country’s surveillance efforts, but it’s clear that the novel H1N1 virus causing the disease has made solid headway in Japan, which has 350 confirmed cases, the most outside of the Americas. Cases over the past few days have also nearly doubled in Chile to 74, the highest number yet seen in the Southern Hemisphere. Still, WHO’s Keiji Fukuda, the assistant director-general, explained at a press conference today that the spread does not merit moving from a phase 5 alert to phase 6, which would indicate a full-scale pandemic. “It’s quite possible that it will continue to spread and it will establish itself in many other countries in multiple regions, at which time it would be fair to call it a pandemic,” said Fukuda. “Right now, we’re really still in the early parts of the evolution of the spread of this virus, and we’ll see where it goes.”

WHO earlier had defined phase 6 as sustained community spread of the virus in two regions of the world but last week put that definition on ice, following pressure from member countries that criticized the phasing system for not taking into account disease severity. Fukuda said in the next few weeks that WHO hopes to hold a videoconference with prominent scientists and public health specialists who have “a wide range of opinions” about how to define phases in influenza outbreaks. “We’re trying to see what kind of adjustments might be made to make sure that the definitions really meet the situation,” said Fukuda.

At a press conference held today by the U.S. Centers for Disease Control and Prevention (CDC), the agency’s top scientific spokesperson, Anne Schuchat, pointed to indicators that suggested the worst may be over in the United States—for now at least. “Our national statistics and most of our regional statistics suggests that we may have passed the peak here for this time of year,” said Schuchat.

CDC does not have hard evidence that the novel H1N1’s spread has actually declined. Rather, CDC divides that United States into nine regions, and seven have seen a decrease in influenza-like illness (ILI) over the past few weeks. “We were over the baseline for this time of year—which is really extraordinary—for the past several weeks, and now we’re down below the baseline again,” said Schuchat. But she cautioned that the drop may just be a “respite” because of the coming of summer and that the virus may return in full force when the cold weather returns in the fall.

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