How the Black Death spread
1. People were infected when they were bitten by a flea carrying the plague germ
2. The fleas carrying the germs lived on black rats, which infested the ships on trade routes between Asia and Europe
3. The rats came ashore off the ships and spread the disease inland
4. Fleas on humans, as well as body lice, may have carried the germ and helped to spread the disease through bedding and clothing