 It is generally thought Filipinos possessed immunity to many of the Old World diseases that devastated American populations  Due to trading contacts with mainland Asia where some acute infections became endemic in the Christian era  Acute Infections Smallfox Measles Inluenza  The existence of immunity to such diseases in the Phils. has been generally been inferred from the absence of a dramatic decline in the population following European contact

 Palaeopathological studies of Filipino populations are few  In any case of skeletal remains can only provide limited insight into the incidence of acute infections  Circumstancial Evidence is very important  Three main lines of investigation The existence of written sources The existence of unusually large number of early dictionaries in native Filipino languages Examination of the pattern and level of mortality with these acute infections

 Reasons The demographic collapse of native peoples in the America is generally attributed by the acute infections Spread through face-to-face contact Not dependent on the existence of an insect, rodent, or other vector for their propagation Short period of infection can lead to death Americas sixteenth – century epidemics  Acute infections confer life-long immunity on survivors

 Required number of population for these diseases to become endemic Measles – 200,000 to 300,000 people Smallpox – 100,000 to 200,000 people  Below these thresholds and where the population is dispersed,  The spread of disease is slow  “Fade-outs” are common  Immunity can only be acquired where there is constant contact with an external source  The Phil. Pre-Spanish time Population About 1.5 million people Widely dispersed over 7,000 islands Significantly less than 100, 000 people per island Exceptions Panay in the Visayas -- Luzon the largest island --

 Populations in different islands and regions did not form and generate the number of susceptible necessary to maintain acute infections  As a result, epidemics were dependent on acute infections being introduced from regions where they were endemic  Some may have arrived from other islands in the Southeast Asian archipelago where populations were of sufficient size to act as “boosters” in maintaining the chain of infection

 Chinese sources indicate that smallpox arrived in china in the fourth century and had become endemic in the 11 th century  Two centuries later it had established in Japan  There is some doubt that it had become established in Japan prior to the arrival of Europeans  Measles probably arrived in China about the same time as smallpox  By 1500 China had also been affected by epidemics of influenza, mumps, and chickenpox, and possibly plague and typhus.

 Contacts between these regions and the Southeast Asian archipelago were increasing thereby greatly expanding opportunities for their spread  China’s distance to the Phils. is miles, could take as six to eight days, though often longer  China’s travel to Japan take only seven to eight days  Several hundred crews and passengers that generally travelled on these trading vessels could easily maintain acute infections during the short journeys.

 At the time of Spanish arrival about ships were coming annually from mainland China  While Japanese raider-traders occasionally frequented the west and north coast of Luzon  There is little doubt that opportunities existed for the introduction of acute infections from the Asian mainland  Even though acute infections may have arrived in the Phils. From China and Japan, they may not have spread widely through the islands due to geographical and social barriers to their spread

Manila Mindoro Cebu Mindanao Jolo  Trades established channels into the interior through which diseases might be introduced  The population was dispersed and communications between and within the islands were slow  So many diseases would have died out before they reached a new group of people to infect

 This pattern of frequent “fade-outs” meant that acute infections did not become endemic in the islands and therefore Filipino populations could not acquire immunity to them through constant exposure