Kissing and cancer

By Razib Khan | May 21, 2011 11:39 pm

I recently listened to Paul Ewald talk about how a lot of cancer is due to infection on the radio show To the Best of Our Knowledge. That wasn’t too surprising, Ewald has been making the case for a connection between infection and lots of diseases for a while. What jumped out at me is his claim that kissing can spread some of the viruses. Here’s something he told Discover a few years back:

D: How do we get infected with these dangerous pathogens?

PE: Two of the most powerful examples are sexual transmission and kissing transmission, and by that I mean juicy kissing, not just a peck on the cheek. If you think about these modes of transmission, in which it might be a decade before a person has another partner, you realize that rapidly replicating is not very valuable—the winning strategy for the microbe would be to keep a low profile, requiring persistent infections for years. So we would expect that disproportionately, the sexually transmitted pathogens would be involved in causing cancer, or chronic diseases in general. You can test this. Just look at the pathogens that are accepted as causing cancer—Epstein-Barr virus, Kaposi’s sarcoma–associated herpesvirus, human T lymphotropic virus 1—and find out whether they’re transmitted this way. They almost all are. A random sample would yield maybe 15 to 20 percent of pathogens associated with cancer being sexually transmitted, yet the figure is almost 100 percent. When you look at viruses alone, it is 100 percent.

If a lot of kissing and number of sexual partners is predictive of risk of cancer, my immediate thought is that this naturally explains a lot of the cancer that  runs in families. Families can pass on genes and cultural norms which would favor or disfavor certain behaviors.

MORE ABOUT: Cancer, Disease

Comments (13)

Links to this Post

  1. A couple links « A Pastor's Notes | May 23, 2011
  1. Ian Tindale

    That does it! I’m never touching a radio again.

  2. dave chamberlin

    We are constantly breathing and frequently eating but slow acting infections only enter our body by swapping tongues and new sexual partners. The man could be right, I am no expert, but I hope he is wrong. It will be a worse world when cheap thrills become a slow motion plague.

  3. John Emerson

    While saliva is teeming with microorganisms of various kinds, normal urine is sterile. So if health is the main concern for you, golden showers should be your preferred expression of intimacy.

  4. Darkseid

    yeah, i remember that interview really well. it stuck in my head because i’d never heard anything like it before. also, the newest thing you’ve probably seen is that oral sex is now the biggest cause of oral cancer:
    Razib, post that new radio interview if it has anything to add to the original Discover one – i’d like to hear it.

  5. mn

    Ah, just wondering if the cancer that’s contracted from the HPV is more likely transmitted orally by ingesting semen into the mouth, throat, etc. or if transmission is just as likely if there’s no ejaculate involved.

  6. Families could also perhaps pass on bacteria. Vaginally born babies seem to mainly inherit bacteria from their mother’s feces and vagina (not necessarily the *exclusion* of other inoculations or to an effect on relative proportions induced by diet and other factors, but nevertheless a heritable component), but I imagine that kissing and various sexual activities could all make some contribution, depending on specific sexual activities.

    I have a blog post related to this:

    Is the Intestinal Microbiome Part of Our Genome?


  7. More evidence that the killjoy fuddy-duddies displaced by the sexual revolution were right all along.

    The next couple of bits sounded like stuff someone might make up to mock NPR.

  8. dave chamberlin

    Now I have to go out and buy “Plague Time, A New Germ Theory of Disease” by Paul Ewald. I want to know more.

  9. mn

    Ewald & Ewald-Cochran= on the money over a decade ago

    Now, they’ve established a link between h. pylori and Parkenson’s

  10. Muhr

    To add onto Chris’ comment, cavity causing bacteria can be passed on by kissing.

  11. pconroy

    I have GERD, so take meds against H.Pylori – so am I better off or not?

  12. Mthson


    HPV is easy to transmit by contact with genital tissue and surrounding tissue (not blocked by condoms), and I’d assume ejaculate as well.

    Men and women with minimal sexual history should consider getting the $500 vaccination before they’re exposed.


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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at


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