How can a virus be determined to cause a disease? From other posts I have read here, humans carry hundreds of different strains of viruses. How is a study structured and carried out to determine that one virus is the cause of a disease, and not any of the other viruses present? Any examples of studies are greatly appreciated as well.
- SARS virus is found in people suffering from SARS, and not found in those who are healthy.
- The virus can be isolated from infected people and grown in cell cultures (here, Vero cells).
- Viruses grown in culture can be reisolated and compared with (and found identical to) the suspected pathogenic virus.
- This isolated virus can re-infect people (or infect model organisms; in this case, a species of macaques).
- Virus in reinfected organisms can be isolated, grown in culture, and found identical to the original pathogen.
- The immune system is observed to respond in similar ways to the infection (pneumonia and lung tissue lesions).