What are the causes of disease based on Koch's postulate?

The microorganism or other pathogen must be present in all cases of the disease

the pathogen can be isolated from the diseased host and grown in pure culture

the pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal

the pathogen must be reisolated from the new host and shown to be the same as the originally inoculated pathogen

--the pathogen can be isolated from the diseased host and grown in pure culture

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