The people most affected by the flu were:
More men than women
Unlike other outbreaks of flu, the 1918 epidemic decimated not the young and the old, but those between the ages of 15 - 38. Men were more severely affected than women, possibly because they moved around more and were exposed to the viral infections to a far greater degree.
The Influenza Epidemic Commission surmised that the older population was partially immunised having lived through previous infections.
Particularly hard hit were pregnant women. Spontaneous miscarriages were frequent amongst expectant mothers who had been infected. As the disease was fatal to so many potential parents, school enrollments reflected a marked drop in the mid-twenties, a fact ascribed by Cape Educational authorities to the significantly lower birth rates during and after the flu epidemic. Phillips indeed speaks of "a lost generation".
The population of the Cape appeared to bear the brunt of this epidemic as shown by the figures below:
Percentage of deaths by province:
Cape Province - 62,46
Transvaal - 20,55
OFS - 6,98
Natal - 10,01
Of those who died, close on 80% were black, many living in rural areas of the Transkei and Ciskei.
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.