A passenger virus is a virus that is frequently found in samples from diseased tissue, such as tumours, but is not a contributing factor in 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 might be passenger only rather than a causative agent includes: A well-established example is lactate dehydrogenase virus, which is often found in mouse tumours.
[2][3] It has also been suggested that a virus related to Alcelaphine herpesvirus 1 is a passenger virus that, unlike AHV1 itself, does not cause bovine malignant catarrhal fever.
[4] The discredited[5] Duesberg hypothesis posits that HIV is a passenger virus in the etiology of AIDS.