The disease cases must be epidemiologically linked (that means that medical staff are able to establish definite links between the cases), as opposed to occurring by coincidence.
Izehlo zesi sifo kufuneka zibe nonxulumano lwendyikityha yesifo esithile esosulelayo (oko kukuthi abaxelengi bezonyango kufuneka babe bayakwazi ukufumana unxulumano oluqinisekileyo phakathi kwezehlo), kunezo zehlo ezizenzekelayo ngexesha elinye.