Health experts are warning the world to prepare for a major pandemic. But the experts say they just do not know when it will strike. A special health monitoring group gave the warning to world leaders last week at the United Nations General Assembly. The group said the next pandemic could move around the world in as little as 36 hours. It said the disease could kill up to 80 million people and cause serious economic losses. The group is called the Global Preparedness Monitoring Board. It operates independently of the World Health Organization and the World Bank. The board was set up last year to prepare a yearly report on the possibility of a pandemic. The first report was frightening. The group notes improvements in medicine over the years. But it adds that politics and social issues keep people in both rich and poor countries from much needed medical care. And it says this threatens the whole world.