Revised WHO pandemic scale requires higher incidence of disease for most alert levels by ProQuest

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									  CMAJ                                                                                                              News
Revised WHO pandemic scale requires higher incidence of
disease for most alert levels
Early release. Published at www.cmaj.ca         a forgone conclusion,” (www.who.int                  countries in one region. In the old guide-
on Apr. 28.                                     /csr/disease/influenza/pipguidance2009               lines, the spread was “still localized,
                                                /en/index.html).                                     suggesting that the virus is becoming in-


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     n the midst of global concern                  Overall, the revised scale appears to            creasingly better adapted to humans, but
     about a potential A(H1N1) swine            require more cases of human infection                may not yet be fully transmissable.”
     influenza pandemic, the World              for each step up a level. For example,                  Whether on the new or old scale,
Health Organization (WHO) has re-               the old guidelines for Phase 3 stated                Phase 6 is essentially a global pan-
vised its 6-point scale for determining         that there could be “at most rare in-                demic, in which a virus has caused sus-
whether a pandemic is a possibility.            stances” of human-to-human spread,                   tained outbreaks in 2 or more countries
    Using the revised scale, the WHO’s          while the new scale (Box 1) says that                in 1 WHO region and a sustained out-
Emergency Committee (which classi-              while the virus may have caused “spo-                break in at least 1 country in another
fies outbreaks as part of its responsibili-     radic cases or small clusters” of dis-               WHO region.
ties under the 2005 International Health        ease, that has not been sufficient “to                  The WHO indicated on its website
Regulations) on Apr. 27 raised the              sustain community-level outbreaks.”                  that the revisions to the pandemic alert
swine influenza pandemic alert level to         The capacity to cause such community-                scale were prompted by a greater under-
Phase 4 from Phase 3. The revised               level outbreaks is now the standard for              standing of what a pandemic is and how
scale indicates that Phase 4 is charac-         Phase 4 designation. In the old guide-               to respond to one. That understanding
terized by sustained human-to-human             lines, the spread was “highly localized,             was garnered from responding to the
transmission of a virus that is able to         suggesting that the virus is not well                avian flu outbreak, which began in 2003,
cause community-level outbreaks. The            adapted to humans.”                                  and to an “increased understanding of
new WHO guidance document states                    The revisions are most pronounced                past pandemics, strengthened outbreak
that “Phase 4 indicates a significant in-       for Phase 5 alerts. The new guidelines               communications, greater insight into dis-
crease in risk of a pandemic but does           state that a Phase 5 alert will be declared          ease spread and approaches to control,
not necessarily mean that a pandemic is         when a virus has spread into at least 2              and development of increasingly sophis-




 On Apr. 27, the WHO raised the swine influenza pandemic alert le
								
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