The World Health Organization has called it a "public health emergency of international concern."
Seemingly out of nowhere, the swine flu virus has spread from person to person in Mexico and the United States, triggering global concerns as governments scramble to find ways to prevent further outbreak.
Q. What is swine flu?
A. Swine influenza, or flu, is a contagious respiratory disease that affects pigs. It is caused by a type-A influenza virus. Outbreaks in pigs occur year-round.
The most common version is H1N1. The current strain is a new variation of an H1N1 virus, which is a mix of human and animal versions. Read full article »