This curve presents the physician a nice and credible insight of the behaviour of bacteria when they arrive at a suitable environment for their growth. The only thing bacteria can do in such “favorable” environment is that they grow and divide. By doing so, from a pure conservative view-point, they keep their species and make every possible chemical change they may think of to that environment; guilty they are: still no one can say.
The lag phase may represent the incubation period after which the disease is apparent. The exponential phase may correspond to the acute phase of illness. The stationary phase may show that the patient is going to overcome the causative organism. The death phase may represent a convalescence from disease. This nice bacterial growth curve would show the physician and the patient that cure should be the rule for most bacteria-caused diseases provided that no inappropriate measures or interferences are given chance.
Useful reference: online Wikipedia.