During the mumps and Japanese B encephalitis (JBE) epidemics of 1947–1948 there were 46 known cases of encephalitis among the Guamanian civilian population, with 43 survivors of the acute illness, giving a case fatality of 6.5 per cent overall. Two deaths occurred among the 27 patients diagnosed as having JBE (7.4%). Follow-up examinations were made more than 9 years after the acute illness on all 32 of the survivors who still live in Guam and in six of the 11 other patients who have moved elsewhere.
Twenty-three of 25 survivors of JBE, 11 of 14 survivors of mumps encephalitis (ME), and all 4 survivors of an unknown type of encephalitis were examined. All survivors not examined were known to be living at the time of this study and on the basis of available information are presumed to be well. The frequency of neurological or psychiatric sequelae in all survivors at the time of follow-up examination was at least 40 per cent (11 per cent severe; 29 per cent mild) for JBE; 22 per cent (all mild) for ME; all survivors of the unknown type of encephalitis had neurological abnormality at the time of follow-up. The sequelae noted in the survivors of JBE, in decreasing frequency, were: pyramidal-system involvement, mental retardation, impairment of cortical sensory association, psychiatric complaints, brain-stem syndrome, cranial-nerve lesion, muscle atrophy and convulsions.
Only three patients with ME had sequelae and these were very mild. Two had bilateral Babinski reflexes, which suggests that ME may be one reason for the occasional presence of this pathological reflex in otherwise normal people.
Sequelae were much more common in the patients who were less than 10 years of age at time of onset of JBE. Infants had more severe sequelae than older children.
The presence of convulsions and other signs of neuronal involvement during the acute illness correlated well with the later presence of sequelae of JBE. Other symptoms and signs such as elevated temperature, vomiting, and spinal-fluid changes were not of particular prognostic significance.
The high case fatality (33% or higher) and the low sequelae rates reported in the Japanese studies (3 to 14%) contrast with the report of encephalitis cases in this study. The excellent medical care available to the population of Guam may account in part for the low mortality and the high incidence of sequelae reported here. This care may have been responsible for the survival of many patients with severe damage to the brain who would have succumbed under other conditions of hospitalization.
Epidemiologist, Guam Field Station, National Institute of Neurological Diseases and Blindness (NINDB), Guam Memorial Hospital, Agana, Guam.
Chief, Epidemiology Branch, NINDB, National Institutes of Health, Bethesda, Md.