Dosen ökar i takt med att infektionen blir värre.

Because both nouns are in the definite singular form: dosen = the dose, infektionen = the infection.

Both dos and infektion are en-words in Swedish, so their definite singular form usually ends in -en:

• en dos → dosen
• en infektion → infektionen

Swedish uses the definite form directly on the noun, instead of adding a separate word like English the.

Ökar is the present tense of the verb öka, meaning increase.

So:

• öka = to increase
• ökar = increases / is increasing

In Swedish, the present tense often ends in -r, so dosen ökar means the dose increases.

I takt med att is a common expression meaning:

• as
• in step with
• at the same rate as

It connects two developments that happen together. In this sentence, it shows that the dose increases as the infection gets worse.

Literally, takt is something like pace or rhythm, so the idea is in pace with the infection getting worse.

Here, att is part of the fixed expression i takt med att.

It is not the infinitive marker like in att äta = to eat. Instead, it helps introduce a clause:

• i takt med att infektionen blir värre

So you should learn i takt med att as one whole linking expression.

Because blir värre means gets worse / becomes worse, which shows a change over time.

• bli = become / get
• värre = worse

So:

• infektionen blir värre = the infection gets worse
• infektionen är värre = the infection is worse

The second version sounds more like a comparison with something else, while blir värre emphasizes that the condition is worsening.

Yes. Värre means worse, and it is a comparative form.

It is an irregular word, and learners often notice that it does not look like a normal comparative. In contexts about illness, pain, or a situation getting worse, värre is very common:

• Det blir värre = It gets worse
• Smärtan blir värre = The pain gets worse

So in this sentence, infektionen blir värre means the infection is becoming worse.

Because att introduces a subordinate clause, and Swedish subordinate clauses normally do not use the main-clause V2 word order.

So the normal order is:

• subject + verb
• infektionen blir värre

This is different from main clauses, where Swedish often puts the verb in the second position.

A useful comparison:

• Main clause: Dosen ökar
• Subordinate clause: att infektionen blir värre

If there were a sentence adverb, you would see the subordinate-clause pattern even more clearly:

• att infektionen inte blir värre

Yes. You can also say:

I takt med att infektionen blir värre ökar dosen.

That version is completely natural. The meaning is the same.

But notice the word order in the main clause after the opening phrase:

• I takt med att infektionen blir värre ökar dosen
• not I takt med att infektionen blir värre dosen ökar

This happens because Swedish main clauses follow the verb-second rule.

It is quite common and natural, especially in written or explanatory language. It can sound a little more formal or structured than plain när in some contexts, because it specifically suggests that two things change together.

So:

• när infektionen blir värre = when/as the infection gets worse
• i takt med att infektionen blir värre = as/in step with the infection getting worse

The version with i takt med att highlights the gradual parallel change more clearly.

Yes. A common alternative is a ju ... desto ... structure, for example:

Ju värre infektionen blir, desto mer ökar dosen.

That means something like the worse the infection gets, the more the dose increases.

The original sentence is a bit more neutral and direct, while ju ... desto ... makes the proportional relationship more explicit.