Epidemics of a severe, highly lethal encephalitis were reported in eastern Australia during the summers of 1917 and 1918, the first in Queensland and New South Wales (N.S.W.) and the second additionally involving the Murray Valley, including northern Victoria. Enterprising journalists quickly linked the two events, arguing that the mosquito-borne myxoma virus, deliberately introduced to control the rabbit population, must be the same mosquito-borne virus causing encephalitis and death in humans. Attempts to recover virus from usually inadequate pathological specimens failed, although two showed histological evidence of encephalitis. Serological surveys of aborigines and Caucasians following the 1951 epidemic provided abundant evidence that flaviviruses were enzootic-endemic in northern Australia and the lowlands of Papua New Guinea. Migrating birds pay scant attention to Wallacea, and superficially at least, there seems no reason why Japanese encephalitis should not be introduced every spring.