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. 2003 Jun;4(Suppl 1):S47–S52. doi: 10.1038/sj.embor.embor849

Table 1. Examples of biological warfare during the past millennium.

Year Event
1155 Emperor Barbarossa poisons water wells with human bodies, Tortona, Italy
1346 Mongols catapult bodies of plague victims over the city walls of Caffa, Crimean Peninsula
1495 Spanish mix wine with blood of leprosy patients to sell to their French foes, Naples, Italy
1650 Polish fire saliva from rabid dogs towards their enemies
1675 First deal between German and French forces not to use 'poison bullets'
1763 British distribute blankets from smallpox patients to native Americans
1797 Napoleon floods the plains around Mantua, Italy, to enhance the spread of malaria
1863 Confederates sell clothing from yellow fever and smallpox patients to Union troops, USA

It is not clear whether any of these attacks caused the spread of disease. In Caffa, the plague might have spread naturally because of the unhygienic conditions in the beleaguered city. Similarly, the smallpox epidemic among Indians could have been caused by contact with settlers. In addition, yellow fever is spread only by infected mosquitoes. During their conquest of South America, the Spanish might also have used smallpox as a weapon. Nevertheless, the unintentional spread of diseases among native Americans killed about 90% of the pre-columbian population (McNeill, 1976).