In the last two decades, the implosion of African economies under the burden of debt, the negative repercussions of the structural adjustment programs, the crisis of legitimacy, civil wars, and the collapse of some states resulted in a serious health crisis across the continent. Newly emerging diseases, such as Ebola virus and HIV / AIDS, killed and disabled millions. Some "old diseases" such as yellow fever, tuberculosis, and polio, have reappeared. Malaria, cholera, and meningitis continue to kill thousands. In many countries, the medical infrastructure has collapsed, while an increasing number of physicians and nurses have migrated to more hospitable places.