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Malaria - and its cousin, yellow fever - had significant implications during the war and the debilitating consequences of the disease were already certain before the Civil War had started in earnest and well before its final history had been written.
Yellow fever is a potentially fatal viral infection that's transmitted by mosquitoes in tropical regions. In mild cases the symptoms are similar to influenza, but serious cases develop a high temperature and may have a series of after effects, such as internal bleeding, kidney failure and meningitis.