“…However every year there are a few autochtonous cases, diagnosed as being due to Plasmodium vivax, some of them with atypical, very mild and transitory clinical symptoms. These present low parasitaemia, of very short duration, frequently clearing even before a treatment can be initiated (Carvalho et al 1988). These malaria cases are generally concentrated in a few foci, part of them located in the Vale do Ribeira and at the Serra do Mar (Carvalho et al 1988, SUCEN 1990.…”