The effects of the introduction of Eurasian diseases upon an immunologically naïve population can perhaps be best illustrated by the example of the Hawaiian Islands. Not only were the islands of King Kamehameha I geographically isolated, but firm data for the decline of Hawaiian population has survived. A sophisticated island culture that evolved over a period on thousands of years had been reduced, in little more than a century, to a society on the brink of extinction.
When Captain James Cook stumbled upon the Hawaiian archipelago in 1778, the chain boasted a population of between 500,000 and 800,000 people. While he might have been preceded by Spanish galleons on their journeys between Mexico and the Philippines, Cook was the first Pacific explorer to leave a record of reaching Hawaii. He revisited the region one year later to discover the remainder of the major islands, dropping anchor in Kealakekua Bay on the Big Island. He named the cluster of islands the Sandwich Islands in honor of the Earl of Sandwich.
The first recorded disease epidemic, referred to in local tradition as oku’u, occurred on the Hawaiian Islands in 1804. This outbreak may have been typhoid fever, since high fever was accompanied by severe gastrointestinal symptoms. Hawaiian oral tradition estimated that over one-half the population died during this epidemic; King Kamehameha himself suffered (but survived) from the deadly illness. The King’s military forces, which were massed in preparation for an attack on Kauai, suffered devastating losses, as over two-thirds of the soldiers died before the disease ran its course.
The Hawaiian monarchs traveled to London in 1823 to visit King George IV, taking up residence at the Caledonian Hotel after a six-month journey. King Liholiho and Queen Kamamalu visited theaters, dined with leading dignitaries, and acquired a variety of European goods for their palace. In addition, they acquired something unanticipated, which was a relatively mild (for Europeans) childhood disease: measles. Unfortunately for the immunologically-naïve Hawaiian sovereigns, measles proved to be fatal; the King and Queen died in July 1824 in London.
The simultaneous introduction of measles, whooping cough, and a strain of influenza dealt a triple blow to native Hawaiians in 1848-49; the death rate of the sick during this period was estimated at 10%. On the heels of this disease wave came smallpox; the 1853 outbreak had a mortality rate in excess of 20 percent.
From an estimated population of 500,000 persons in 178, the number of indigenous Hawaiians dwindled to 40,014 in 1884; this represents a decline in population of 91.99% in slightly more than a century. What is even most striking about these census figures is that the population figures include persons of partial Hawaiian ancestry.
The arrival of tuberculosis most likely coincided with that of Cook’s ships in 1778; according to expedition records, numerous shipmates were afflicted with this malady. In a previously unexposed population, the mortality rate of tuberculosis has been demonstrated to be approximately 10%.
Another pathogen entered the Hawaiian environment, perhaps as early as Cook’s voyage in 1778, which not only extracted a high death toll but also depressed birth rates: syphilis. The island chain had become a major stopover in Pacific expeditions for provision replenishment, repairs, and shore leave. A physician, William Hillebrand, summed up the ravages of this disfiguring and sometimes deadly disease:
…[this is] no random assertion, but one based on experience and approximative calculation, that in 10 natives, 9 have been infected with this disease [syphilis] at one time or another in their life.
Thus, the experience of the Hawaiian Islands mirrors those of indigenous groups throughout the Americas: an immunologically-naïve native population, through the introduction of Eurasian diseases, underwent depopulation rates as high as 95% during the first century after contact. Any inherited immunity to the new diseases among the natives did not express itself as a regenerative factor in such populations until numerous generations had passed.
This is an excerpt of a book project I am working on, which focuses on the role of epidemic disease in history.