Newspaper, magazine, and journal articles that you read on your topic may cite statistics from other sources. Whenever possible, you will want to track those statistics back to the source to assure their veracity. Use the bibliography to help you find the source of the statistics.
There are several sources for U.S. health statistics, from nonprofit groups trying to cure a disease to a variety of federal agencies, but the Centers for Disease Control is the closest thing to an umbrella organization for this data.
The World Health Organization has created this gateway page, the Global Health Observatory, for the statistics it has compiled on health in countries around the world. Note that many health statistics are not available for developing countries. There is also a lengthy time lag for many of the statistics published by the agency.
The Virginia Division of Health Statistics provides state-level data, and often down to the county/city level.