A passenger virus is a virus that is frequently found in samples from diseased tissue, such as tumours, but does not contribute to causing the disease.
Proving that a virus has no causative role can be difficult. Although none of the following signs is definitive, evidence that a virus found in diseased tissue is a passenger rather than a causative agent includes:
injection of the virus into healthy animals without causing disease;
the absence of the virus at the earliest stages of the disease;
curing the viral infection using antiviral drugs or vaccination with no effect on the course of the disease.
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^ Potharaju NR, Potharaju AK (2006) Is Chandipura virus an emerging human pathogen? Arch Dis Child 91: 279–280 (PMID 16492900) (full text)
^ Duesberg P, Rasnick D. (1998) The AIDS dilemma: drug diseases blamed on a passenger virus. Genetica 104: 85–132 (PMID 10220905)
