In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: BACKGROUND : Dilated cardiomyopathy ( DCM ) and myocarditis occur in many HIV - infected individuals , resulting in symptomatic heart failure in up to 5 % of patients .
### Output Text:
BACKGROUND : Dilated cardiomyopathy ( DCM ) and myocarditis occur in many HIV - infected individuals , resulting in symptomatic heart failure in up to 5 % of patients . 