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: Cases of delayed hemolytic anemia have been described after treatment with injectable artesunate , the current World Health Organization ( WHO ) - recommended first - line drug for the treatment of severe malaria .
### Output Text:
Cases of delayed hemolytic anemia have been described after treatment with injectable <span class="chemical">artesunate</span> , the current World Health Organization ( WHO ) - recommended first - line drug for the treatment of severe malaria . 