malaria

1. Air infected with some noxious substance capable of engendering disease; esp., an unhealthy exhalation from certain soils, as marshy or wet lands, producing fevers; miasma.
2. (Med.) A human disease caused by infection of red blood cells by a protozoan of the genus Plasmodium, giving rise to fever and chills and many other symptoms, characterized by their tendency to recur at definite and usually uniform intervals. The protozoal infection is usually transmitted from another infected individual by the bite of an Anopheles mosquito.

The morbific agent in malaria is supposed by some to be a vegetable microbe or its spores, and by others to be a very minute animal blood parasite (an infusorian).