A bird flu virus never before found in humans has grabbed world attention this week after it infected and killed people in China. Scientists have been scrambling to understand how it happened and, more importantly, whether it poses a risk to public health or could potentially spark a global pandemic.
The good news is that so far there's no sign that the H7N9 virus is spreading from person to person, but experts say it has mutated in a way that has left them a bit worried. Here's a crash course in Bird Flu 101 to help explain what's known about the strain and why it matters:
