Disease and immunity in the pre-Spanish Philippines

It is generally asserted that Filipino populations did not suffer the same demographic collapse that followed Spanish conquest in the Americas because they had previously acquired immunity to Old World diseases through trading contacts with Asia. This assertion is examined by trying to establish which diseases were present in the islands in pre-Spanish times and whether populations there could have acquired immunity to them. This is done through an analysis of the evidence for the presence of infections in China and Japan in particular and the existence of trading contacts with and between the Philippine islands. The likelihood of immunity being acquired is addressed first through a discussion of the physical and human geography of the islands and what is known of the epidemiology of individual diseases from modern scientific research. Second, it reviews evidence from early colonial documents and Filipino dictionaries for the presence and impact of Old World diseases in the early colonial period. The study suggests that Filipino populations had not acquired significant immunities to acute infections in pre-Spanish times, and that their limited demographic impact in the colonial period derived more from the particular geography of the islands. It suggests that in terms of its disease history, the Philippines had more in common with the Pacific islands than mainland Asia, and that the microbiological boundary between the Old World and the New is better conceived of as a broad zone.