The U.S. government has declared swine flu to be a public health emergency.
It remains to be seen how severe swine flu will be in the U.S. and elsewhere, but countries worldwide are monitoring the situation closely and preparing for the possibility of a pandemic.
The World Health Organization has not declared swine flu to be a pandemic. The WHO wants to learn more about the virus first and see how severe it is and how deeply it takes root.
But it takes more than a new virus spreading among humans to make a pandemic. The virus has to be able to spread efficiently from one person to another, and transmission has to be sustained over time. In addition, the virus has to spread geographically.
