Kulingana na Benki ya Ulimwengu, kuna aina za dawa 100,000 hivi ulimwenguni pote, zitengenezwazo kutokana na dutu amilifu zaidi ya 5,000.
normal availability of equipment, i.e. allowance should be made for periodic closures, for paid holidays, for routine maintenance and, where applicable, for the seasonal availability of electricityjw2019 jw2019