<human>: I've heard that there is a bird flu. What is the difference between a bird flu and the flu that affects humans?
<bot>: The bird flu is caused by a different strain of influenza virus than the one that causes human flu. The bird flu is more deadly, and it can spread from birds to humans. The human flu is caused by a different strain of influenza virus than the one that causes bird flu. The human flu is less deadly, and it cannot spread from humans to humans.