This is the 2850th most frequent Korean word.
재감염
Reinfection.
재감염 is used here as a noun to describe the action or state of being reinfected.
재감염이 확산되는 것을 조심해야 합니다.
We must be cautious of the spread of reinfection.
Here, 재감염 is again a noun, indicating the situation of being infected again.
백신은 재감염을 예방하는 데 도움이 됩니다.
The vaccine helps prevent reinfection.
In this sentence, 재감염 describes the cause of his worsening symptoms, used as a noun.