Usage of「感染する」

細菌に感染する showed up in Shin Kanzen Master.
What I don’t understand is why it’s not 感染される.
I found this article that says 感染する is intransitive, but it doesn’t take を. Apparently there are other verbs that accept に but not を in the same way (乗る).

細菌が僕を感染する :x:
僕が細菌に感染する :white_check_mark:

バスが僕を乗る :x:
僕がバスに乗る :white_check_mark:

Is it appropriate to say 彼が感染した to mean “he was infected?”
If anyone can explain the weirdness of this verb to me it would be very much appreciated.

Intransitive verbs don’t take を, because there is no direct object.
Intransitive verbs can use に to mark an indirect object

to be infected by…

乗る is intransitive, so also does not use を

What do you mean by not “感染される”? As in, why is it not written in the passive conjugation? I think that would be a question of the difference between passive and intransitive.

Many intransitive verbs have a definition of “to be something…” (閉まる、付く、etc.)

Here is some thing on passive vs. intransitive: grammar - Difference between intransitive and passive? - Japanese Language Stack Exchange


There’s no madness. As you said (and the article said), it’s intransitive, so it does not take the を. The verb it is translated into in English in the case of the article is transitive, which may be the reason of your confusion…

Yeah, I don’t really see anything odd that would be confusing here.

@Leebo @Naphthalene @audball Thank you guys for your help. I think I’m closer to understanding it now.

I guess I’m just having a hard time wrapping my mind around how 感染する can be intransitive by itself because of the English “infect.” Maybe I should just give it some time to sink in and then try thinking about it again.

It’s also confusing because other intransitive する verbs are more like English. For example, 敵に挑戦する doesn’t mean “to be challenged by an enemy,” but “to challenge an enemy,” while 細菌に感染する means “to be infected by bacteria.” Is there some intrinsic difference between these two verbs or is it just an English issue?

Maybe I just don’t see the disconnect with the English?

“to be infected with flu”


“to infect flu”

With 挑戦する, you could think of it as “to take/bring a challenge to an enemy”

But either way, the answer is probably to just not think about it in terms of English. Japanese people don’t.

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I think @charlesfm meant “flu infects you” Sounds like an “in soviet russia” joke

Yeah, that’s the thing. The same idea has no reason to be expressed with similar grammatical structures, so

Just don’t think about it. You can use it as a crutch if you need to, but in this case it’s probably more confusing than helping…

We don’t say that though… “Hey, Naph looks down today, what happened” “Oh, flu infected him.” Very strange.

To be fair, we don’t say “he’s infected with flu” in conversation either, but only because it’s stiff, not because it sounds strange in English.

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Well, yeah, but it’s grammatically a transitive verb, even if you usually use it in the passive tense.
And I work with biologists, “the virus infected the tissues” is a thing I heard before. (Caveat: not from a native speaker)

True, but it shouldn’t be news to anyone that the passive in English and intransitive in Japanese overlap in translations. That’s pretty normal.

And yes, obviously if you’re making the infectious agent the subject of the sentence then it’s normal. But that’s not what’s going on with 感染する.


Does anyone know of a good dictionary that lists the transitivity of する verbs?

The transitivity should come through in the definition. At least it does for 感染.



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Ok, makes sense thanks :slight_smile:

I don’t know many dictionaries that list transitivity for most words anyway. But they should have examples too which will further expand on the transitivity.

I have 広辞苑 (at my girlfriend’s apartment), which has verb transitivity, but I don’t think it has する verb transitivity. I can check on the weekend.

Adding that I find helpful for these.

Search に挑戦する or any verb and it provides helpful fragments and usage with different particles.

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One note to be careful with this type of thing (the Japanese refer to these circumstances as be動詞 + 分詞):

“The flu infected him.” Transitive, Active.
“He was infected by the flu.” Transitive, Passive
“He was infected with the flu.” Intransitive, PARTICIPLE (not actually passive unless you mean that both he AND the flu were infected).

As the first example is transitive, 感染する cannot produce this translation accurately from a grammatical standpoint.

The second statement would translate to 感染された from a grammatical standpoint, though, we don’t really say this in either English or in Japanese.

The third statement would translate to 感染した from a grammatical standpoint.

In English, we use the past participle in combination with the verb “to be” in order to create an intransitive statement. We shift the transitivity from the participle to the transitive “to be,” allowing for the use of a transitive verb without an agent.

However, we also use “to be” with the past participle to create the passive voice. However, unlike the the intransitive usage of this construction, we are able to add an agent through a prepositional clause, most commonly beginning with “by.”

In cases where “by” does not function, you know that you shouldn’t use an intransitive passive in Japanese: You can be frightened by someone, you cannot be afraid by someone, and the context is very different whether you can or cannot be scared by someone.

One example I know where I do hear 感染される is viruses of the electronic kind (computer or phone virus). I think, since you never actually see the viruses or bacteria that make you sick, it just feels weird to place agency on them. It’s not like they’re out to make you sick or kill you, after all (well, bacteria, at least just want to survive and reproduce; viruses are a different story).

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