Transmission of infectious diseases, post-1492
The last portion of BIO230 surveys a number of infectious agents, and the diseases that they can cause. Notably, a number of these contagions have had a significant effect on the shift of world events. Probably everyone is at least passingly familiar with the Black Death, or Bubonic Plague, and it’s effects on European and Asian history throughout the Middle Ages. And for better or worse, the appearance of retroviruses such as HIV in the latter part of the 20th century has had and will continue to have an incredible effect on US domestic and foreign policy as we continue to deal with the repercussions of this pandemic.
The mingling of European and American cultures following the voyages of Columbus resulted in the introduction of at least two significant diseases into populations that had previously not been exposed to the pathogens. The introduction of smallpox into American populations has been very well documented. The first documented case in the Americas was in 1507 on the island of Hispaniola (present day Dominican Republic/Haiti) by Spanish settlers, and spread to the mainland by 1520. The disease rapidly spread through native American populations, with a fatality rate of over 80% in some cases. According to Wikipedia, smallpox was the single most significant cause of native American deaths from 1780 to 1870. It is important to note that these populations had the exact same innate and adaptive immunities that European populations had at the time, and that the high mortality rates were likely due to failures in public health measures. Interestingly, smallpox received its name from another disease that is also associated with the voyages of Columbus.
Syphilis, or the “Great-pox,” is a disease caused by a spirochete bacterium, unlike smallpox which is caused by a virus. Most epidemiologists agree that syphilis was present at an endemic level in the Americas prior to 1492, and descriptions in European history before this date are poorly documented at best. This has led to the proposal of the Columbian Exchange theory where sailors returning to Europe from the New World introduced syphilis into European populations. Supporting this premise is a well-documented outbreak in Naples, Italy in 1494.
Some epidemiologists maintain that syphilis was present in Europe prior to 1492. Examination of skeletal remains from an English friary dating from the 13th century have shown bone lesions characteristic of chronic syphilis, although the dating of these remains is contested.
Finally, some epidemiologists hold that a combination of the above led to the European syphilis outbreaks of the 16th century, where a preexisting poorly virulent disease (yaws) became significantly more virulent coincidentally. Yaws is another disease caused by a related spirochete bacterium that produces relatively benign lesions, transmitted via direct contact through breaks in the skin. A shift in virulence of a “proto”-syphilitic spirochete potentially explains the emergence of this disease in Europe at this time.