UNITED NATIONS (Reuters) - Avian flu will mutate and become transmissible by humans and the world has no time to lose to stop it becoming a pandemic, the head of the U.N. World Health Organization said on Thursday. Lee Jong-wook, a South Korean doctor, delivered his stark warning as the United States worked to rally states behind a new U.S. plan to fight the disease, which has already killed more than 60 people in Asia and spread to Russia and Europe. "Human influenza is coming, we know that, and no government, no leaders can afford to be caught off-guard," Lee...