U.S. health officials are preparing intensively to combat an anticipated wave of outbreaks of the new H1N1 flu when children return to school and the pace of cases picks up.

Identified by scientists just three months ago, the new swine-flu virus has reached nearly every country, spreading tenaciously with what the World Health Organization this week called "unprecedented speed." Rather than die down in the summer as some experts initially expected, it is continuing to proliferate even in countries like the U.S.