The Geneva-based World Health Organization on Wednesday raised its alert level for the fast-spreading swine flu to its next-to-highest notch, signaling a global pandemic could be imminent.
The move came after the virus spread to at least 10 U.S. states from coast to coast and swept deeper into Europe.
"It really is all of humanity that is under threat during a pandemic," said WHO Director General Margaret Chan. "We do not have all the answers right now but we will get them."
In the United States, President Barack Obama mourned the first U.S. death, a Mexican toddler who had traveled with his family to Texas. Total American cases surged to nearly 100, and Obama said wider school closings might be necessary.
In Mexico, where the flu is believed to have originated, officials said Wednesday the disease is now confirmed or suspected in 159 deaths, and nearly 2,500 illnesses.
The WHO said the phase 5 alert means there is sustained human to human spread in at least two countries. It also signals that efforts to produce a vaccine will be ramped up.