The World Health Organization declared the first flu pandemic in 41 years, even as it stressed there are no signs the H1N1 virus has turned more lethal as it spreads across the globe. The declaration Thursday by the United Nations agency requires countries not yet exposed to the new influenza strain to roll out pandemic-prevention plans and step up monitoring efforts. It also will likely accelerate efforts to develop a vaccine, expected to take several months. WHO Director General Margaret Chan said the "overwhelming majority" of people diagnosed with the virus since it surfaced in Mexico in April experienced mild...