Viruses isolated in Trinidad and Brazil have been found to be related to California encephalitis virus. By various serological tests (complement - fixation, hemagglutination - inhibition and neutralization tests) it has been shown that the South American viruses are all of one type (Melao), related to but separable from not only California encephalitis virus but also the as yet unnamed virus isolated by Eklund from Aedes trivittatus. These three viruses have no direct relationship to any previously described group of viruses. They are, however, indirectly related to the Bunyamwera group through an intermediate virus—Guaroa, isolated in Colombia. Guaroa is related to the Bunyamwera group by CF (but not by HI) and to the California viruses by HI (but not by CF).
It is proposed to recognize the separation between the California viruses and the Bunyamwera group by according the California viruses the status of a complex.