MULTIPLE-SCLEROSIS IN THE FAROE-ISLANDS .5. THE OCCURRENCE OF THE 4THEPIDEMIC AS VALIDATION OF TRANSMISSION

Based on 32 cases with clinical onset 1943-73, we previously described the occurrence of clinical neurologic multiple sclerosis (CNMS) on th e Faroe Islands as constituting three consecutive epidemics, with 20, 9, and 3 cases respectively. As of 1991 there were seven additional ca ses of CNMS with clinical onset 1984-1989 constituting the fourth epid emic, as well as three more members of epidemic III. We have proposed that CNMS is the rare late result of infection with PMSA (the primary multiple sclerosis affection), a state requiring some two years of exp osure from age 11+ for acquisition by Faroese, and that PMSA was first transmitted during World War II by affected but asymptomatic British troops to Faroese residents; part of this (F1) cohort of affected asym ptomatic Faroese transmitted PMSA to the next (F2) cohort comprising F aroese reaching age 11 in the interval when that F1 subset was present , and the F2 cohort similarly transmitted PMSA to the third (F3) cohor t. Cases of CNMS defining epidemic I-III were members of the respectiv e F1-F3 cohorts. The existence of epidemic IV within the F4 cohort of Faroese may be taken as validation of our transmission models and of o ur theses as to the nature of multiple sclerosis.