По сравнению с прошлой зимой я болею реже, но этой весной у меня уже второй бронхит.

По сравнению с is a fixed expression meaning compared with or in comparison with.

It is followed by the instrumental case, which is why you get:

• с прошлой зимой = with last winter

So:

• По сравнению с прошлой зимой = Compared with last winter

This is a very common pattern in Russian:

• по сравнению с прошлым годом = compared with last year
• по сравнению с летом = compared with the summer

In Russian, some time expressions can appear in the instrumental case without a preposition to mean during a season or period of time.

So:

• прошлой зимой = last winter
• этой весной = this spring

This is very natural Russian.

You can compare:

• зимой = in winter
• весной = in spring
• летом = in summer
• осенью = in autumn

And with adjectives:

• прошлой зимой = last winter
• этой весной = this spring
• холодной зимой = during a cold winter

So the instrumental here is not random: it is a normal way to express time with seasons.

This is a very common learner question.

Болеть can mean to be ill, but in context it can also describe someone’s general tendency to get sick or be sick from time to time.

Here:

• я болею реже literally means I am ill less often
• in natural English, that often becomes I get sick less often

So Russian uses болею because it is talking about repeated illness in general, not one single completed event.

If you said я заболеваю реже, that would sound more like I fall ill less often, but болею реже is very natural and common.

Реже means more rarely or, in natural English, less often.

It is the comparative form of редко:

• редко = rarely
• реже = more rarely / less often

So:

• я болею редко = I get sick rarely
• я болею реже = I get sick less often

Russian often uses comparative adverbs like this:

• часто → чаще = often → more often
• редко → реже = rarely → less often
• поздно → позже = late → later

Both are possible.

• Я болею реже
• Я реже болею

Both mean essentially the same thing: I get sick less often.

The version in your sentence, я болею реже, sounds very natural and neutral. Russian word order is flexible, and the choice often depends on emphasis.

Very roughly:

• я болею реже puts the comparison/result at the end
• я реже болею gives a little more prominence to реже

In this sentence, я болею реже flows nicely after по сравнению с прошлой зимой.

Russian often uses у меня to talk about conditions, symptoms, illnesses, or things happening to a person.

So:

• у меня бронхит = I have bronchitis
• у меня температура = I have a fever
• у меня кашель = I have a cough

In your sentence:

• у меня уже второй бронхит literally means I already have a second bronchitis
• in natural English: this is already my second case/bout of bronchitis this spring

This is a very idiomatic Russian way to say it.

Your alternative, я уже болею бронхитом второй раз, is understandable, but it sounds less natural here.

Because Russian is talking about the second occurrence in a sequence, not just the number two.

• второй бронхит = the second case/bout of bronchitis
• два бронхита = two bronchitises/cases of bronchitis

In English, we also usually prefer this is my second bronchitis this spring or better my second case of bronchitis, rather than just two bronchitises.

So второй is more natural because it means:

• one happened before
• now this is the next one

The word уже strengthens that idea: already the second one.

Yes, in a sense.

Russian very often omits есть or another obvious verb in the present tense when the meaning is clear.

So:

• у меня (есть) бронхит
• у меня уже второй бронхит

The sentence is complete and natural without a verb.

You can think of it as an elliptical structure meaning something like:

• У меня уже второй случай бронхита
• Это уже второй бронхит у меня этой весной

But Russian normally leaves that unstated.

Уже means already.

In this sentence, it adds a feeling of surprisingly early repetition or unfortunately, again:

• этой весной у меня уже второй бронхит = this spring I’m already on my second bout of bronchitis

So уже suggests:

• spring is not over yet
• and this has happened again sooner or more often than expected

Without уже, the sentence would be more neutral:

• этой весной у меня второй бронхит = this spring it’s my second bronchitis

With уже, it sounds more emphatic.

Because бронхит is the main noun in the expression у меня второй бронхит.

The structure is basically:

• у меня = with me / I have
• второй бронхит = a second bronchitis / second case of bronchitis

Here второй agrees with бронхит in:

• masculine
• singular
• nominative

So:

• второй бронхит

If the noun changed, the adjective would change too:

• вторая простуда = a second cold
• второе воспаление = a second inflammation

Here it means one episode / one case / one bout of bronchitis.

In Russian, disease names can sometimes refer either to:

1. the illness in general, or
2. a particular case of it

In this sentence, because of второй and этой весной, it clearly means a particular occurrence:

• my second bout of bronchitis this spring

That is why the whole sentence sounds natural even though English often prefers to add a word like case or bout.

Но simply means but.

It introduces a contrast:

• По сравнению с прошлой зимой я болею реже
  = Compared with last winter, I get sick less often

• но этой весной у меня уже второй бронхит
  = but this spring I’m already on my second bout of bronchitis

So the contrast is:

• overall, things are better than last winter
• but this spring is still going badly in one specific way

That makes но very appropriate here.

That is close word-for-word, but it is not natural English.

A better translation would be:

• Compared with last winter, I get sick less often, but this spring I’ve already had bronchitis for the second time.

Or:

• Compared with last winter, I get sick less often, but this spring this is already my second bout of bronchitis.

The Russian sentence is natural, but English usually needs small adjustments like:

• less often instead of more rarely
• second bout/case of bronchitis instead of second bronchitis

Yes. Russian word order is flexible.

For example:

• Но этой весной у меня уже второй бронхит
• Но у меня этой весной уже второй бронхит
• Но у меня уже второй бронхит этой весной

The first version is the most natural here because it sets the time frame early:

• but this spring...

That helps the sentence contrast neatly with прошлой зимой in the first part.