Article doesn't indicate any “public works” evidence but for the large hole of a mass burial. First assumption, based on the offered sparse details, suggests all were buried as part of one event, which may have spanned a few days, a week or so. This is Africa, heat and carrion eaters make short work of exposed bodies thus supporting the tight time frame. Absent evidence of layering, an epidemic seems to be a better starting hypothesis.
“If one hears the sound of hoof beats in Africa, one can expect zebras or buffalo, certainly not horses.”
Location, location, location.
Anthrax...........................