The problem of sickness, and the disastrous effect it could have on sailors in the West Indies, was well known before the outbreak of war in 1739. The dangers had been graphically illustrated by the fate of Admiral Hosier's expedition in 1726. Sent to the Caribbean to prevent the Spanish treasure ships sailing from Porto Bello, Hosier had blockaded these ships for six months, until sickness finally forced him to return to Jamaica. When he arrived there he had 622 men sick out of a rated complement of 1920. Having recruited new men, he then proceeded to lose them in a further six–month blockade of Vera Cruz and Havana. In the end the total losses exceeded 4,000, with Hosier falling a victim in August of 1727. Little had changed by 1739 and as Lloyd and Coulter wrote –

The combined operations of the war of 1739–48 and the continued presence of fleets in the Caribbean were to emphasise this over and over again, and prove that sickness was the greatest enemy to be faced in this area.

It was a problem that applied equally to Jamaica and the Leeward Islands. From an administrative point of view, the only difference was that of scale. Jamaica, as the most important base, had far more men serving there and this was reflected in the greater numbers who fell sick. It was this difference in scale that led to different methods being used to care for the sick in the two commands.