Researchers have proposed that the herpes virus responsible for the childhood illness roseola may cause a type of T cell leukemia. Ninety percent of the population has been infected by the virus by two years of age, but the T cell leukemia is relatively

Question

rare. The virus can be cultured in the laboratory in tissue culture, but not in mature organisms. Discuss the obstacles to applying Koch's postulates to the etiology of this disease.

What will be an ideal response?

Answer 1

Koch's first postulate, that the suspect agent must be present in every case of disease, is met, but far more people have the virus than have the disease. This suggests that more than the presence of the virus is necessary for the leukemia to develop, and the additional factors may be difficult to identify. The third postulate states that the isolated suspect agent must cause disease when introduced into a host. This situation presents two difficulties in satisfying the third postulate. The first is that it is unethical to deliberately expose humans to an agent that may produce life-threatening disease (the leukemia). Additionally, ethical concerns aside, because such a large percentage of the population has been exposed to the virus, a large pool of potential uninfected subjects does not exist.
Bloom's Taxonomy: Analysis
Section: The Nature of Infectious Disease
Learning Outcome: 14.13