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: It remains to be seen whether such pre - existing antiviral mutations could result in widespread emergence of HBV resistant strains when lamivudine - containing highly active antiretroviral ( ARV ) treatment ( HAART ) regimens become widely applied in South Africa , as this is likely to have potential implications in the management of HBV - HIV co - infected patients .
### Output Text:
It remains to be seen whether such pre - existing antiviral mutations could result in widespread emergence of HBV resistant strains when <span class="chemical">lamivudine</span> - containing highly active antiretroviral ( ARV ) treatment ( HAART ) regimens become widely applied in South Africa , as this is likely to have potential implications in the management of HBV - HIV co - infected patients . 