The World Health Organization (WHO) is coordinating the global response to human cases of H5N1 (Bird) flu and monitoring the threat of a H5N1 (Bird) flu pandemic. Epidemiologists use monitoring data to predict where and how disease might spread. It is important to know where disease outbreaks not only begin in the world, but also how and where they might spread in the United States. A primary goal of flu monitoring is to identify any outbreak of human-to-human transmission quickly so health officials can attempt to contain and control the outbreak.