Urgent opportunistic observations: the study of changing, transient and disappearing phenomena of medical interest in disrupted primitive human communities.

Two newly identified foci of usually rare disease occurring in high incidence in isolated primitive populations of West New Guinea are discussed as examples of medical problems that demand immediate intensive investigation because the unique naturally occurring experiments they represent are soon likely to be altered. These are: (1) amyotrophic lateral sclerosis, Parkinsonism, and dementia syndromes in a small population of Auyu and Jakai peoples in the Lowlands, and (2) an epidemic of burns from cysticercosis epilepsy from newly introduced Taenia solium in pigs in the Ekari people of the Wissel Lakes in the Highlands. A third new example is a focus of male pseudohermaphroditism among the Simbari Anga in the Highlands of Papua New Guinea. These are presented along with a series of eleven further examples of the kind of problems that require urgent opportunistic observation because of the extreme changes that investigation and therapeutic and preventive efforts themselves, as well as the inevitable effects of acculturation, will evoke from the moment an investigator or other outsider from a technologically advanced culture enters the previously isolated community.