Bacteria with facial expressions illustration

Evidence that Viruses Cause Disease

Koch’s postulates are the following:

  1. The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
  2. The microorganism must be isolated from a diseased organism and grown in pure culture.
  3. The cultured microorganism should cause disease when introduced into a healthy organism.
  4. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

These postulates were proposed by Thomas M. River in 1973 to establish the role of a specific virus as the cause of a specific disease. These postulates are the modifications of Koch’s postulates.

  1. The viral agent must be found either in the host’s (animal or plant) body fluids at the time of disease or in cells showing lesions specific to that disease.
  2. The host material with the viral agent used to inoculate the healthy host (test organism) must be free of any other microorganism.
  3. The viral agent obtained from the infected host must –
    – Produce the specific disease in a suitable healthy host
    And/or
    – Provide evidence of infection by inducing the formation of
    antibodies specific to that agent.
  4. Similar material (viral particle) from the newly infected host (test organism) must be isolated and capable of transmitting the specific disease to other healthy hosts.