The spread of a disease doesn't stop at a country's borders. With more people traveling to other countries and living in crowded cities, it's easier for germs to spread. Infectious diseases that start in one part of the world can quickly reach another. Drug resistance is on the rise, making it harder to treat certain diseases. Natural and man-made disasters create refugee populations with immediate and long-term health problems.

Some of the major diseases currently affecting countries around the globe include AIDS, malaria, pandemic/avian flu, and tuberculosis. Many countries and health organizations are working together and sharing information on these and other health issues.