Question

a. Zika virus exposure during pregnancy has been associated with microcephaly in newborns. Koch’s postulates are traditionally used to link a pathogen to a disease. List three reasons why Koch’s postulates are not completely applicable in this case.

b. List two major differences between viruses and bacteria.

Answer 1

A. Koch postulates cannot be applied to viruses because -

They cannot be cultured in nutrient media in the labs.

The same virus is able to cause disease with different sign and symptoms in different individuals.

There are ethical restrictions to culture viruses using humans as model organisms.

B.

Viruses are noncellular entities which have a proteinaceous capsid as the outermost covering whereas bacteria are cellular organisms having phospholipid plasma membrane as outermost covering.

The genetic material in viruses is either RNA or DNA but in bacteria it is always DNA.

Viruses are all pathogenic but bacteria may or may not be pathogenic.

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