who found the real cause of yellow fever
Yellow fever In 1848, Josiah C. Nott suggested that yellow fever was spread by insects such as moths or mosquitoes, basing his ideas on the pattern of transmission of the disease.[86] Carlos Finlay, a Cuban doctor and scientist, proposed in 1881 that yellow fever might be transmitted by mosquitoes rather than direct human contact.[87][88] Since the losses from yellow fever in the Spanish–American War in the 1890s were extremely high, Army doctors began research experiments with a team led by Walter Reed, and composed of doctors James Carroll, Aristides Agramonte, and Jesse William Lazear. They successfully proved Finlay's ″mosquito hypothesis″. Yellow fever was the first virus shown to be transmitted by mosquitoes. The physician William Gorgas applied these insights and eradicated yellow fever from Havana. He also campaigned against yellow fever during the construction of the Panama Canal. A previous effort of canal building by the French had failed (in part due to mortality from the high incidence of yellow fever and malaria, which killed many workers).[10]
Feodosia It is believed that the devastating pandemic the Black Death entered Europe for the first time via Kaffa in 1347, through the movements of the Golden Horde. After a protracted siege during which the Mongol army under Janibeg was reportedly withering from the disease, they catapulted the infected corpses over the city walls, infecting the inhabitants, in one of the first cases of biological warfare. Fleeing inhabitants may have carried the disease back to Italy, causing its spread across Europe. However, the plague appears to have spread in a stepwise fashion, taking over a year to reach Europe from Crimea. Also, there were a number of Crimean ports under Mongol control, so it is unlikely that Kaffa was the only source of plague-infested ships heading to Europe. Additionally, there were overland caravan routes from the East that would have been carrying the disease into Europe as well.[8]