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: HBV lamivudine - resistant strains were detected in 3 of 15 mono - infected chronic hepatitis B patients and 10 of 20 HBV - HIV co - infected patients .
### Output Text:
HBV <span class="chemical">lamivudine</span> - resistant strains were detected in 3 of 15 mono - infected chronic hepatitis B patients and 10 of 20 HBV - HIV co - infected patients . 