Malaria has had a profound influence on ancient Greek history. Describe what this disease is and discuss this influence, especially the reasons for its impact.

In the early 20th century, a doctor and a classicist (controversially) argued that the decline of Ancient Greek civilization was caused by malaria.
Malaria, Italian for “bad air,” is a parasitic disease spread by the female Anopheles mosquito. A mosquito is infected when it bites an infected human. The parasites it ingests with its blood meal replicate and grow in the mosquito. After 10–18 days, the parasites can be found in the insect’s saliva. The parasites are injected with the saliva when the mosquito takes a blood meal from another human. Mosquitos and malaria thrive in tropical and subtropical climates—warm, humid regions without much temperature variation. In humans, malaria causes flu-like symptoms: fever, chills, fatigue, and mental-status changes.
Sir Ronald Ross, a physician awarded the Nobel Prize in Physiology or Medicine for identifying the mosquito as a malaria vector, believed the mountain valleys, fountains, and streams that surrounded villages in Ancient Greece were ideal breeding grounds for the Anopheles. In his introduction to classicist W.H.S. Jones’s 1909 book, Malaria, a Neglected Factor in the History of Greece and Rome, Ross supports Jones’s theory that the decline of Ancient Greek civilization was predicated on the spread of malaria throughout the region.
Jones believed that malaria was brought to the Mediterranean in the fourth century B.C. by “soldiers, merchants, or slaves coming from Africa or Asia” (9). He argues that symptoms of the disease led to less activity in cities, a decrease in intellectual vigor, decaying patriotism, sentimentalism in art and pessimism in philosophy (15). “By 300 B.C.,” he writes, “the Greeks had lost much of their manly vigour and intellectual strength” (15). The fall of a great civilization, all because of a mosquito.
https://archive.org/details/malarianeglected00jonerich

https://www.cdc.gov/parasites/malaria/index.html