Relationship between prevalence and intensity of Opisthorchis viverrini infection, and clinical symptoms and signs in a rural community in north-east Thailand. - Upatham ES; Viyanant V; Kurathong S; Rojborwonwitaya J; Brockelman WY; Ardsungnoen S; Lee P; Vajrasthira S (Bulletin of the World Health Organization, 1984)