Smallpox in Americas

CODEX Entry 6016: Smallpox in Americas


Some believe that the death of 90–95% of the native population of the New World was caused by Old World diseases. It is suspected that smallpox was the chief culprit. In 1519 Hernán Cortés landed on the shores of the Aztec Empire. In 1520 a second group of Spanish arrived from Hispaniola, bringing with them the smallpox. Cortés defeated them, but one of his men contracted the disease. During the Aztecs rebellion against Cortés, the Spanish soldier carrying smallpox died. By the time Cortés returned to the capital the following year, smallpox had killed most of the Aztec army and 25% of the population. As a result Cortés easily defeated the Aztecs and reentered Tenochtitlán. The Spaniards said that they could not walk through the streets without stepping on the bodies of smallpox victims. The effects of smallpox on the Inca empire were even more devastating. Beginning in Colombia, smallpox spread rapidly before the Spanish invaders even arrived. Within months, the disease had killed the Incan Emperor Huayna Capac, his successor, and most of the other leaders. Francisco Pizarro, much like Cortes, was able to take advantage of civil strife and deceits to capture the leader and his best general. Within a few years smallpox claimed between 60% and 90% of the Inca population. In 1561, smallpox reached Chile by sea, when a ship carrying the new governor Francisco de Villagra landed at La Serena. Chile had previously been isolated by the Atacama Desert and Andes Mountains from Peru, but the natives lost 20 to 25 percent of their population. The Spanish historian Marmolejo said that gold mines had to shut down when all their Indian labor died.

In 1633 in Plymouth, Massachusetts, the Native Americans were struck by the virus. As it had done elsewhere, the virus wiped out entire population groups of Native Americans. It reached Mohawks in 1634, the Lake Ontario area in 1636, and the lands of the Iroquois by 1679. A particularly virulent sequence of smallpox outbreaks took place in Boston, Massachusetts. From 1636 to 1698, Boston endured six epidemics. In 1721, the most severe epidemic occurred. The entire population fled the city, bringing the virus to the rest of the Thirteen Colonies.

During the 1770s, smallpox killed at least 30% of the Northwestern Native Americans.


The last major smallpox epidemic in the United States occurred in Boston, Massachusetts throughout a three-year period, between 1901–1903. During this three-year period, 1596 cases of the disease occurred throughout the city. Of those cases, nearly 300 people died. As a whole, the epidemic had a 17% fatality rate. In an effort to control the outbreak, the Boston Board of Health began voluntary vaccination programs. Individuals could receive free vaccines at their work places or at different stations set up throughout the city. By the end 1901, some 40,000 of the city’s residents had received a smallpox vaccine. However, despite the city’s efforts, the epidemic continued to grow. In January 1902, a door-to-door vaccination program was initiated. Health officials were instructed to compel individuals to receive vaccination, pay a $5 fine, or be faced with 15 days in prison. This door-to-door program was met by some resistance as some individuals feared the vaccines to be unsafe and ineffective. Others felt compulsory vaccination in itself was a problem that violated an individual’s civil liberties. In 1905 the Supreme Court upheld the law, indicating no citizen can refuse mandatory vaccination.