It is generally regarded that the malaria receptive area of the Northern Territory is north of the 19th parallel ie. a line just north of Tennant Creek. This line is based on historical evidence of previous outbreaks of malaria in the N.T. It is possible that malaria could once again become endemic ie. permanently established north of this line. Before 1962, when endemic malaria was eradicated from the N.T., there were numerous outbreaks in the Top End of the N.T. north of the 19th parallel. Malaria was not just restricted to the higher rainfall areas of the Top End.