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Generally, viruses are infectious in nature and there are several cancer-causing viruses that are known (i.e. oncovirus)

My question is: Are these oncoviruses infectious in nature? If so, what is the way in which they can be transmitted?

(edit:just a background to connect the title and the question (as mentioned by user iayork):While reading my text(which led me to the doubt) I was considering the virus as a causal organism and the disease as cancer(malignant tumour cells).The cancer cells are non-contagious however I wanted to understand if the disease was.Thus I was interested on the routes of the transmission of the viruses.Also note (which I had already asked user Chris in the comment) "most cancer disease are non contagious but if cancer disease was due to virus if it was contagious or not"

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  • $\begingroup$ You may want to reword the title so that it matches the question. It should be something like "Can viruses that cause cancer be contagious?". Otherwise it sounds like you're asking if the cancer itself is contagious, which is a totally different question. I see your edit, but the ambiguity still remains. $\endgroup$
    – JBentley
    Commented Aug 31, 2017 at 9:53
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    $\begingroup$ Just to be clear, not sure whether you understand this part or not, but viruses that "cause" cancer do not guarantee cancer, they increase the risk of cancer in affected individuals. $\endgroup$
    – Bryan Krause ♦
    Commented Aug 31, 2017 at 15:42

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The question title and the question itself ask two slightly (but critically) different questions.

  • Can cancers caused due to viruses be contagious? NO
  • Are these oncoviruses infectious in nature? YES

The tumors caused by the viruses are not contagious. You can't take the tumor and transfer it to a new host and see a new cancer. The viruses that cause the tumor are contagious, but in many cases by the time the tumor has arisen the viruses are no longer in a contagious form. A tumor that's caused by HPV doesn't have contagious virus in it (see explanation below), and you can't transplant the tumor into a new host. There still may be contagious virus present in the patient, but the tumor itself is not contagious.

Explanation HPV causes cancer by having a part (and only a part) of its genome integrated into the host genome, so cancers associated with it inevitably have a defective virus genome. There could theoretically be infectious virus in the neighboring tissues, but the cancer is driven by non-contagious virus. See for example The role of integration in oncogenic progression of HPV-associated cancers for a fairly basic explanation

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    $\begingroup$ I think your answer is pointing us to a language problem. You as a biologist may think that "a cancer" is a synonym for "a tumor" and so you wrote an answer geared towards this interpretation. For a member of the general public, "a cancer" can well be "the disease a person with tumors has" which is contagious at some stages. Maybe this should be made more explicit before people without enough background are totally confused. $\endgroup$
    – rumtscho
    Commented Aug 30, 2017 at 14:01
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    $\begingroup$ @rumtscho That is not the general public definition of cancer, and it is not contagious at any stage in humans. $\endgroup$
    – Bryan Krause ♦
    Commented Aug 30, 2017 at 15:01
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    $\begingroup$ Generally tumors are not contagious, but we know of at least one case where that is not true. A communicable facial tumor has decimated tasmanian devil populations, though it is spread through an allograft, not a virus. en.wikipedia.org/wiki/Devil_facial_tumour_disease $\endgroup$
    – BlackThorn
    Commented Aug 30, 2017 at 23:18
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    $\begingroup$ there is also evidence of contagious cancers in clams sciencemag.org/news/2016/06/… $\endgroup$
    – Stephen Thomas
    Commented Aug 30, 2017 at 23:45
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    $\begingroup$ Since the question is about viral tumors, it's probably actively confusing to start talking about non-viral contagious tumors like the bivalve and Devil versions. $\endgroup$
    – iayork
    Commented Aug 31, 2017 at 0:20
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Yes, Oncoviruses are infectious in nature. A good example is the Human Papilloma Virus, which does not immediately cause cancer, but can cause precancerous lesions in infected regions including cervix, vulva, vagina, penis, anus, mouth, or throat (see references 1 and 2). HPV is transmitted during sexual activities (hence the broad range of infected tissues due to different practices).

There is now a vaccine available since a few years which allows prevention against infections with the HPV types 16 and 18, which cause most of these infections. If it is administered before the first sexual activity, it provides a good protection against infection with these HPV types.

Other tumor viruses like Hepatitis C or Kaposi's sarcoma-associated herpesvirus, to name just two, are also infectious. If they weren't, they wouldn't be able to spread.

As @iawork says, it is important to say that the cancers which are caused by these viruses are not contagious, only the viruses are.

References:

  1. Human papillomavirus (HPV) and cervical cancer
  2. HPV-associated diseases.
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  • $\begingroup$ thank u for the answer.jst to be precise,then can it be said that when we say that cancers are non-contagious it actually excludes a virus caused cancer which is actually infectious? $\endgroup$
    – user 33690
    Commented Aug 30, 2017 at 9:55
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    $\begingroup$ @CATHARANTHUS Normal cancers are not contagious. The either arise due to a genetical predisposition or acquired mutation. The virus is the agent that causes these mutations (which could also be a chemical). It happens to be that viruses are infectious. $\endgroup$
    – Chris ♦
    Commented Aug 30, 2017 at 10:23
  • $\begingroup$ @iayork : Huh... Apparently reading comprehension is not my thing this morning. Meh. Removed. $\endgroup$
    – Eric Towers
    Commented Aug 30, 2017 at 13:18
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    $\begingroup$ @BryanKrause I removed this part of the comment. $\endgroup$
    – Chris ♦
    Commented Aug 30, 2017 at 15:41
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Oncoviruses are most commonly transmitted sexually however in the cases of EBV (Epstein-Barr Virus) and MCV (Merkel cell polyomavirus) can be transmitted in other ways such as through an oral or respiratory route.

These viruses are contagious however as mentioned by others the cancers caused my these viruses are not contagious. In the case of HPV for instance the cancer tends to be caused through the virus integrating with the host cell and expressing two oncoproteins (E6/E7) which interact with tumor-suppressing proteins resulting in uncontrolled cell growth. The virus itself cannot bind to live tissue it instead is limited to the basal cells of stratified epithelium such tissue can be found in the cervix which is why HPV is responsible for upwards of 90% of cervical cancer cases. Because viral integration usually needs to occur for cancer to occur the virus itself needs to be contracted for integration to occur.

Also as mentioned above two genotypes of HPV (16 and 18) are responsible for most cases of cancer but there are over 200 genotypes of HPV of which there is a large number which are considered oncoviruses such as 31, 33, 39, 45, 52, 58, and 59. And another of others which are still subject to debate - many of which are not covered by the current vaccine.

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