The first wave of the flu followed typical flu symptoms consisting of a three-day fever, a cough and a runny nose, followed by a rapid convalescence.
The second and third waves were often fatal. Of every 1000 people who were infected, 800 had severe flu symptoms. The remaining 200 had lung complications, 120 of whom could be classified as desperately ill or dying.
Normal flu symptoms accompanied by a very high fever, shivering and muscle aches quickly translated into lung complications, sometimes progressing to bronchopneumonia, which sometimes swept through the body like toxaemia or septicaemia. People literally drowned in their own fluids.
Sources for the whole section on the 1918 epidemic in South Africa: SA Railways and Harbour Magazine, December 1918; Phillips, Howard. South Africa's worst Demographic Disaster: The Spanish Influenza Epidemic of 1918. (South African Historical Journal, (20), 1988.