In the spring of 1815, Spain claims an epidemic of yellow fever struck Gibraltar, so that the British authorities built several barracks as field isolation in the neutral zone. On 20 April 1815 Lt. Governor of Gibraltar, George Don agreed with the general commander of the Campo de Gibraltar, General Don José María de Alós, that "a large proportion of the inhabitants Gibraltar to [..] not they suffered fever, temporarily established on the neutral ground, as close as circumstances permit, in front of this fortress".