Ok, in this dictionary, virus is a countable noun.

All the tomato plants are infected with a virus.

But why rice is an uncountable noun while virus is a countable noun though it is so much harder to count "virus" than "rice".

When a virus goes into our body, it can multiply & create a lot of its copies.

I would guess that, in term of language, a virus refers to the whole disease rather than 1 copy of that virus.

If that is the case then language does not reflect clearly reality. It is not as clear as 5 apples or 10 oranges. I mean "a virus is not the same as an apple" because we can say "There are 5 apples (of the same type)" but not "There are 5 virus A (of the same type)".

We can say there are many viruses such as Hepatitis, Tuberculosis, HIV, etc. But I am not sure I can say "There are 5 hepatitis B viruses in his liver".

Can we say "He got infected by a Hepatitis B virus" or "He got infected by 1 million Hepatitis B viruses"

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    @Lambie, there are five different types of hepatitis virus, "A", "B", "C", "D" and "E", and it is not impossible that all five should be present in one liver. Nov 2, 2016 at 13:30
  • @StoneyB, Sorry, I updated my question
    – Tom
    Nov 2, 2016 at 13:35
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    In that case, even though it is conceivable that exactly five individuals of the Hep B species are present in the liver, it is not conceivable that anyone could confidently assert that fact. Nov 2, 2016 at 13:41
  • @StoneyB, you misunderstood what I meant. I meant "a virus is not the same as an apple" because we can say "There are 5 apples (of the same type)" but not "There are 5 virus A (of the same type)".
    – Tom
    Nov 2, 2016 at 13:52
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    @Tom I don't misunderstand; I am merely saying that to speak of "five viruses" of the same species is not ungrammatical, merely unusual. Nov 2, 2016 at 13:57

6 Answers 6


In non-technical English, "virus" can mean either "virus species" or "virus particle". Context usually makes it clear which one you mean.

The problem with saying that "he has five viruses in his liver" is that a viral infection consists of billions of virus particles, and that context means that "five viruses in his liver" would be understood to mean five virus species and not five virus particles. Conversely, if you say that he has "billions of viruses in his liver", it seems very unlikely that he's so careless or unlucky as to have contracted billions of diseases simultaneously, so it would be understood to mean billions of virus particles.

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    +1 Have to say, though, I think you'd probably be dead long before you hit the billion diseases milestone :P
    – Au101
    Nov 3, 2016 at 1:39

There are 5 hepatitis B viruses in his liver

This is valid, if you observed 5 individual viruses in his liver somehow. However only in a scientific context would you hear anything like this.

In a non-scientific context, virus is a singluar thing that has the ability to "spread" and that one "has."

I have the hepatitis B virus.

Many times a plain noun is used as a shortcut for "kind of X" or "type of X". If you mean virus this way, then it's plural if you mean multiple types of viruses, and not restricted to a scientific context.

I have 3 hepatitis viruses (A, B, and C, poor guy)


I am vaccinated against several viruses (TB, hepatitis, etc.)

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    A couple of reasons why you would never hear this in a scientific context. First, the biological term for an "individual virus particle" is virion. Second, there are virtually no circumstances where 5 individual virus particles would be found in a liver. Instead, you'd expect a titer in the millions or billions. Even if you were deliberately infecting a laboratory animal for study, there's virtually no way you would be able to infect with an inoculum of 5 virions. Nor would you want to. As for this issue of types of viruses, these are called serotypes, so you have 3 serotypes of HBV. Nov 2, 2016 at 16:36
  • Many times a plain noun is used as a shortcut for "kind of X" or "type of X". If you mean virus this way, then it's plural if you mean multiple types of viruses, and not restricted to a scientific context. -- Exactly. And you can do this for almost any noun, countable or not, and you can make it plural to mean more than one kind of type. If you compare ancient France to modern France, you are comparing two Frances. Nov 3, 2016 at 1:57
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    But it's very awkward to just say "3 hepatitis viruses" (and "two Frances"). The natural way to say it would be "I have three strains of hepatitis" (and "two eras of France".) Nov 3, 2016 at 4:38

It could be correct, but only under extremely narrow circumstances--ones I'm almost certain you didn't intend.

"Virus" refers to the type of thing. "Five viruses" would, therefore, mean five different types of virus. Qualifying that with "hepatitis B" means you're talking about 5 different varieties of hepatitis B virus.

One of the reasons viral infections are so difficult to treat is that most viruses mutate relatively quickly. So, if you were referring to 5 different mutations of the hepatitis B virus, it could make sense to refer to "5 hepatitis B viruses".

I believe what you're talking about, however, is five of the infectious particles of hepatitis B virus, but all five of them (apparently) alike. In this case, what you're really looking for is the word for an individual infectious particle of a virus, which is "virion". Therefore, the correct phrasing would be: “There are 5 hepatitis B virions in his liver."

  • I disagree. Non-technical English uses "virus" to mean both "virus particle" and "virus species". Nov 2, 2016 at 21:56
  • @DavidRicherby: Maybe I just hang out with excessively technical people, but I can't recall ever hearing anybody refer to a virus particle as a "virus". Sometimes they use words other than virion (e.g., "cell") but not "virus". Nov 2, 2016 at 23:08

When talking about a variety or a type of something, you can use normally uncountable nouns as countable nouns. For example, if you want to say "He grows five kinds of rice on his farm", it's also grammatically correct to say "He grows five rices on his farm"

I'd be more inclined to say "five different rices" as it sounds less ambiguous, however.

However, in your hepatitis B example, I'm not sure in what context you would talk about five individual hepatitis B viruses. Let's say you're looking into a microscope and saw five individual little hep B viruses. In this case, I think it would be totally correct to say "There are five hepatitis B viruses." The meaning of the sentence is just somewhat unclear without any context.

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    You would say "five different rices"? Odd; that sounds much less fluent than "five kinds of rice" to this native US English speaker. It's not impossible to say "rices" but it's one of those words that just almost never comes up.
    – stangdon
    Nov 2, 2016 at 13:52
  • @stangdon I agree; but take a look at this Nov 2, 2016 at 13:55
  • I would think we say "Hepatitis B is A Virus", "HIV is A Virus", "The 2 viruses are Hepatitis B & HIV"
    – Tom
    Nov 2, 2016 at 13:57
  • @StoneyB - "Rices" does occur, but I think it's telling that all of the examples that we've seen so far have been written by non-native speakers.
    – stangdon
    Nov 2, 2016 at 13:58
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    @stangdon Nonetheless, Google easily finds "aromatic rices", "specialty rices", "A Guide to the Rices of Asia", "What's the deal with all the rices? Which one is best?" and other uses which don't trouble me at all. Nov 2, 2016 at 14:09

You can count viruses, but the implied meanings are much different.

I have a virus.

Read as: I'm ill. It doesn't mean I have one virus in my body, or many of one particular type.

I have 5 [types of] Hepatitis B viruses in my liver

Sounds somewhat clumsy but is arguably "valid" except for a small sophistry: It means you have five different serotypes of HBV, and there exist only four (that's really nitpicking, though... I will not go on nitpicking about tuberculosis being a virus). It does not mean you have a total count of five viruses.

The reason why I say it sounds somewhat "clumsy" is that you do not generally have the virus in your liver, but you just "have it" (in your liver, yes, but also in your serum and some other bodily fluids), or you "are positive on", or you "suffer from". The difference between the last and the last but one being that you are not ill in the former case (at least, not necessarily, but you can still infect others) whereas you are ill in the latter case.

It is perfectly valid to "count" viruses otherwise, only just it is not done so often in everyday conversation. Note by the way that it is not valid to count virii because Latin doesn't know a plural for virus (which is poison/venum, so more substance, not many individual small thingies). So... that doesn't exist. You will nevertheless find virii being used.

For example, this works:

Sneezing, on the average, propels 50 million viruses through the air immediately in front of you. (I made that number up)

Obviously, nobody counts 3 or 5 viruses, but in the millions or as a concentration such as 105 per milliliter, this certainly works, why not.

  • I hope you mean, "I will not go on nitpicking about tuberculosis not being a virus." Nitpicking about nitpicking. Nov 2, 2016 at 16:31

A virus does not resemble an apple.  A virus resembles a fruit. 

If you fill a basked with a half a dozen apples, a half a dozen oranges and a dozen bananas, then I might describe that basket in more than one way:  There are two dozen fruits in the basket.  There are three fruits in the basket. 

In the interest of comparing apples to apples, we may want to compare apple to Hepatitis.  They both exist in a number of varieties, and the Granny Smith is as distinct from the Red Delicious as Hep A is from Hep B.  They each happen to be a member of a broader category, fruits and viruses respectively.  However, the contrast is more interesting.  When we count apples, we count pieces of fruit, not cultivars. If we count Hepatitises, we count the strains, not the particles. 

More importantly, in the interest of comparing apples to oranges, we have more than one countable sense of the word "fruit".  A sentence like "There are three fruits in the basket" uses a sense that means something like "varieties of fruit".  A sentence like "There are two dozen fruits in the basket" uses a sense that means something like "pieces of fruit". 

We also have more than one countable sense for the word "virus".  On the one hand, we can use the word "viruses" to count viral particles.  On the other, we can use the word "viruses" to count viral strains.  Language does not always clearly reflect reality.  In this case, perhaps it does. 

Finally, in the interest of being clear, we rarely use words like "fruit" or "virus" on their own when literally counting.  I could say "three fruits", but I'm more likely to say "three types of fruit", letting the word "fruit" take its uncountable sense.  Similarly, you could say "there are five Hepatitis viruses" and "the sample contains millions of Hepatitis viruses".  You might prefer to say something like "there are five types Hepatitis virus" or "the sample contains millions of Hepatitis virions". 

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