What spread the Black Death?

Related questions

1. Who cured the Black Death?
2. Which is better FTP or SFTP?
3. How many people did the Black Death kill?
4. What did people think caused the Black Death?
5. Is the plague still around?
6. Why did plague doctors have long noses?
7. Is there cure for plague?
8. How did plague doctors cure the plague?
9. How many people died in the Black Death?
10. Did animals die from the Black Death?

Tags

1. #estimated
2. #deaths
3. #black
4. #between
5. #fleas
6. #specifically
7. #million
8. #historians
9. #spread
10. #europe
11. #death
12. #spreading
13. #century
14. #humans
15. #speculated
16. #blamed
17. #around
18. #plague
19. #responsible