Zheng He belongs to the Ming dynasty.
Maybe there were no cures, vaccines, or antibodies at the time. Medicine was never completely discovered for centuries to come, which is why the Black Plague occurred during the medieval/Middle Ages.
Answer:
Developed in the 1830s and 1840s by Samuel Morse (1791-1872) and other inventors, the telegraph revolutionized long-distance communication. It worked by transmitting electrical signals over a wire laid between stations.
