Final answer:
Viral infections are not recognized as a cause of illness among the Ndembu, who instead may attribute illness to ancestral ghosts, magic, or social conflict.
Step-by-step explanation:
The cause of illness among the Ndembu that is NOT recognized is viral infections. The Ndembu, like some other indigenous societies, had a range of explanations for illness and health that included religious, astrological, and supernatural factors. For many indigenous cultures, the idea that illness could be caused by ancestral ghosts, magic, or social conflict was more consistent with their worldview and medicinal practices compared to germ theory, which was not universally recognized or understood. Illnesses were sometimes ascribed to spiritual conditions or social disharmony, rather than to microorganisms like viruses and bacteria.