This is the 895th most frequent Russian word.
заболевания
Diseases.
Here, 'заболевания' is used in its singular form in the genitive case to signify the prevention of a specific disease.
Профилактика заболевания помогает избежать осложнений.
Disease prevention helps avoid complications.
In this context, 'заболевания' is plural and refers to multiple diseases collectively.
Многие заболевания можно предотвратить с помощью вакцинации.
Many diseases can be prevented through vaccination.
Here, 'заболевания' is in the genitive plural, indicating possessive context to describe the treatment of diseases in general.