Translating どこでかまれたのかわかると、どんな虫が原因かわかることがあるので伝えてください。

Question

I was almost towards the end of my bedtime news article when I got stumped by this sentence:

虫の専門家は「虫にかまれて、腫れたり痛かったりするときは、病院に相談してください。どこでかまれたのかわかると、どんな虫が原因かわかることがあるので伝えてください」と話しています。

To Japanese learners past the beginner level, it is known that [辞書形]+ことがある roughly translates to "there are times that~" or "sometimes, ~". Somehow, translating this sentence somehow using that translation doesn't make sense to me. It appears to me that the sentence translate to:

"If you know where you got bitten, you may know what bug was the cause (of the bite) [or "you may know what bug bit you"], so please inform (tell) them."

Something seems to be off in this sentence. (I can't tell why though.) Or should it be translated to

"If they know where you got bitten, they may know what bug was the cause (of the bite) [or "they may know what bug bit you"], so please inform (tell) them."

Is this an example of a sentence with two clauses where the implied subject changes halfway through? And speaking of implied subject, how can one tell in just one reading that the subject has changed midsentence? Or do even native speakers of Japanese have to read a sentence twice just to realize that the subject has changed?

Answer 1

The grammatical subject that corresponds to わかる is actually very explicit; the subject is not "you" nor "they" but どんな虫が原因か, which is an embedded question. 分かる here means "to become known; to turn out" (see the second definition here). For example, 犯人が分かりました means "I found out who the criminal is" rather than "The criminal understood it". This part can be written also as どんな虫が原因かがわかる, but を/が after an embedded question is often omitted.

In the ～が分かる construction, who noticed the fact is not explicitly stated, and it may or may not be inferred from the context. For example, you can say ドアは閉じていたことが分かった ("It turned out that the door was closed") without saying who noticed this fact. In your context, it is obviously the physician who may notice the responsible bug. Therefore, a literal translation is "what bug is the cause sometimes becomes clear", but you can rephrase it like "a physician may notice which bug is the cause".