William Pym was a Scottish surgeon that served with the British army in the West Indies during the Napoleonic Wars. Pym was present during the British occupations of the islands of Guadeloupe, Saint Lucia and Martinique. During the occupation of Martinique between 1794 and 1796, Pym witnessed an outbreak of yellow fever that swept through the army, killing an estimated 16,000 men. This experience gave him an unparalleled knowledge of the disease.

In 1815, he published this treatise on yellow fever (then also known as bulam fever). In it, Pym showed that the disease was highly infectious, more so in warmer climates, and, much like smallpox, would only affect a person once. This meant that if someone survived it, they would be immune from future infection. Pym also noted that the disease did not affect local populations as severely as it did foreigners. On its publication, the book was controversial, but it has now been proven that many of Pym’s conclusions were correct.

In 1826, Pym was made Superintendent-General of Quarantine and two years later was sent to Gibraltar to manage an outbreak of yellow fever there. In gratitude for his efforts, he was knighted by William IV in 1830, becoming a Knight Commander of the Royal Guelphic Order in 1831.