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: METHODS : Thirty - seven of 160 patients who had HCV - genotype 1b , had high virus load , and received 24 - week combination therapy developed anemia with hemoglobin level < 10 g / dl or anemia - related signs during therapy .
### Output Text:
METHODS : Thirty - seven of 160 patients who had HCV - genotype 1b , had high virus load , and received 24 - week combination therapy developed anemia with hemoglobin level < 10 g / dl or anemia - related signs during therapy . 