Well, Flesh Eating and Step are the same kind of bacteria, but they're a different strain and therefore cause different diseases. I can't say the same for Ear Ache or Pneumonia however, b/c they're not different strains but they affect different locations in the body, and so, cause different diseases based on where. Nerve Cell and Brain Cell are both neurons, but the Brain Cell represents a specific neuron, and the Nerve Cell represents the general types of neurons who work with the brain cells by carrying out their messages such as telling the muscle cells to move. Mono, affects both spleen and lymph nodes at the same time, and so only one disease can come from it. But I guess there's nothing wrong in making a different version of the same microbe/disease
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