Now at level five.
Announcing the increased alert level in Geneva, WHO Director General Margaret Chan urged all countries to activate their pandemic plans, including heightened surveillance and infection-control measures.There still seems to be quite a bit of confusion over why the strain seems to be deadly to some and only a mild flu in others. I remember from reading The Great Influenza - a good, but hair-raising read - that the deadly flu of 1919 had waves. The first wave was not so deadly, but the second was. It certainly makes sense to me that if Mexico is the country of origin the virus may be further along there than here, meaning a more damaging version could still be coming to the US and other parts of the world. On the other hand, perhaps this virus just isn't that deadly after all. Mexico is "revising down its death toll" from 20 to 7 involving confirmed swine flu cases. Originally more than 100 deaths were thought to be tied to this virus.
She said action should be undertaken with "increased urgency".
She added: "It really is the whole of humanity that is under threat in a pandemic."
You can follow a map of swine flu infections here.