When the infected sailors abandon ship and swim ashore, the locals assist them out of the water despite Harris' warnings not to touch them. The natives thereupon all get sick as the disease sweeps through the town, but cholera is rarely spread directly from person to person. The most common method of infection is ingesting tainted food or water.
When Harris is before a panel of Japanese leaders to convince them to vote to accept the treaty, he is asked by one if the U.S. imports Africans for slavery. He answers regrettably yes and goes on to say many are trying to end slavery. The story took place around 1858, fifty years after The Act Prohibiting Importation of Slaves of 1807 took effect in 1808.