Panic over Ebola has the makers of dietary supplements aggressively targeting Africans, claiming to have a cure for the lethal virus.

Late this week, both the World Health Organization and the United States Food and Drug Administration issued strong warnings about false Ebola cures. The latter threatened American companies with penalties if they continue making such claims.

Neither agency listed products or companies they accused of fraud or explained why they had acted so suddenly.

Nigeria’s health minister was widely reported on Thursday to have endorsed an American nutritional supplement, one that the W.H.O. said was an example of the sort of “false rumors of effective products” it was trying to quell.