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According to the WHO:

67% of the population are infected with herpes simplex virus type 1 (HSV-1)

Presumably there are other viruses as well that infect a lot of people. How many infections does the average person have?

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closed as too broad by anongoodnurse, AMR, AliceD, The Last Word, March Ho Dec 28 '15 at 12:18

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ What do you mean by "have"? Should we count short-term infections that can be caused by countless cold viruses from many different families? Or should we count persistent viruses only, such as HSV and HPV? $\endgroup$ – Eli Korvigo Dec 27 '15 at 22:54
  • $\begingroup$ @EliKorvigo : I would call all of them. $\endgroup$ – Christian Dec 27 '15 at 23:03
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    $\begingroup$ There isn't really an average person; I doubt this can be answered as asked. If you live on a remote island, you won't have all that many; if you live in an overcrowded city, you'll likely have a ton; if you live in cold regions, your risk of many viruses is lower than in temperate or tropical regions. If you travel a great deal, you're exposed to many more than someone who stays put. Etc., etc., etc. Then there's everything in between. Maybe the only real way to get an answer to this is to look at rates for every known virus and add? I don't know. I think it's too broad. $\endgroup$ – anongoodnurse Dec 27 '15 at 23:37
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    $\begingroup$ You also need to make the distinction between being infected and becoming sick. The immune system can keep infections subclinical, but they will still remain present in the body. $\endgroup$ – AMR Dec 28 '15 at 0:18
  • $\begingroup$ This is likely very different depending on location. Most people live in Asia (China, India) or Africa. Most of the studies are done in North America or Europe. $\endgroup$ – YviDe Dec 28 '15 at 13:00
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Ignoring short-term (acute) viral infections, so only considering persistent viruses, probably on the order of 5-10-ish. There are 8 human herpesviruses known, of which 6 (herpes simplex I, EBV, CMV, VZV, HHV6, and HHV7) are very common in humans, generally infecting 50-90% of a population. There are over 50 strains of human adenoviruses, but only a few are very common and persistent; hAb2 and hAd5 are probably the most likely. Then there may be a human papilloma virus or two persistently infecting many people, though the prevalence is lower than herpes or adenoviruses. So, it's reasonable to assume that most people have somewhere around 5-10 persistent viral infections.

If you add in acute infections, and ask about all exposures during one's life, you're probably looking at thousands or tens of thousands of viruses, but the questions about what's a different virus and what's an "infection" become trickier.

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  • $\begingroup$ I really like the this answer, but can you give a reason for "thousands or tens of thousands of viruses"? $\endgroup$ – anongoodnurse Dec 27 '15 at 23:42
  • $\begingroup$ About a hundred strains each of rhinovirus and enterovirus, plus multiple strains of influenza viruses, noroviruses, adenoviruses, RSV, parainfluenza, rotaviruses, reoviruses, coronaviruses, parvoviruses ... probably around a thousand already, and these are only the agents that have been identified and that are known to cause disease. New pathogens are still being discovered, meaning we're undoubtedly infected with many unknown viruses, and there's very little known about viral infections that don't cause disease, even though those are probably common too. $\endgroup$ – iayork Dec 28 '15 at 3:03
  • $\begingroup$ Thank you for this answer. I'm not an epidemiologist, so forgive me if I am very mistaken, but are you saying that we've all (on average) been infected by a hundred strains of enterovirus? Maybe we have, but that seems a bit high to me. With rhinovirus I won't disagree. I doubt that the "average person" has actually been infected by a great many influenza strains, and the numbers sound too high to me. But I repeat, I'm not an epidemiologist. $\endgroup$ – anongoodnurse Dec 28 '15 at 4:09
  • $\begingroup$ That's why I didn't want to answer that part. Questions of "what's a different virus" and "what's an infection" come down to shrugs and handwaving. As soon as I say something, you focus in on the details, and they don't matter. It makes no difference whether we're infected with 10 or 20 or 50 enteroviruses, because the vast dark matter of viral infections outweighs all of them If you don't like my answer (I'm not an epidemiologist either, just a virologist) then make your own; you can define strains the way you like, and come up with any answer you want. $\endgroup$ – iayork Dec 28 '15 at 12:08
  • $\begingroup$ I didn't intend to offend; I asked because that was the OP's question, and on SE, the answers are supposed to answer the question. If there isn't an answer, I'm certainly not going to try to give one. That was the point of my comments to the OP. $\endgroup$ – anongoodnurse Dec 28 '15 at 14:51

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