The practical difference in the US was pretty much nil, since we have active cases to contend with already, but in some countries this is likely to lead to a stepped-up response.
Because the WHO's pandemic alert level is written into some national pandemic flu plans as a trigger point for specific actions, it is a relevant issue and it's worth considering whether Phase 4 is the right level at this time.
Here is the definition for Phase 4:
Phase 4 is characterized by verified human-to-human transmission of an animal or human-animal influenza reassortant virus able to cause “community-level outbreaks.” The ability to cause sustained disease outbreaks in a community marks a significant upwards shift in the risk for a pandemic. Any country that suspects or has verified such an event should urgently consult with WHO so that the situation can be jointly assessed and a decision made by the affected country if implementation of a rapid pandemic containment operation is warranted. Phase 4 indicates a significant increase in risk of a pandemic but does not necessarily mean that a pandemic is a forgone conclusion.
We certainly seem to meet this criteria with the outbreaks in Mexico, but let's take a look at Phase 5:
Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.
We meet this criteria, as well, with the outbreak in Mexico and laboratory-confirmed human-to-human transmission from husband to wife in Kansas. Both countries are in the Americas Region.
We don't yet meet the criteria for Phase 6 --or at least we can't confirm that we do:
Phase 6, the pandemic phase, is characterized by community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5. Designation of this phase will indicate that a global pandemic is under way.
As they said over at Effect Measure, "... [the] WHO has been timid and slow" in responding to this crisis, and with this decision it seems they're continuing in that pattern.
I realize that there are political and economic costs attached to moving to Phase 5 and that, with the world economy in shambles, this is an especially difficult time for the global community to have to face those costs. But what does it do for the credibility of the WHO when anyone who can read can plainly see that we should be in Phase 5 by the agency's own definition?
The World Health Organization does a tremendous amount of good in the world and they have an important role to play in managing this outbreak. It's time for them to refocus and re-emerge with the courage to do this job as only they can; they should start by following their own guidelines.