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: Given the influx of Southeast Asians into the United States , oxidant medications should be used with caution , especially if an infection is present , in individuals of ethnic backgrounds that have an increased prevalence of hemoglobin E .
### Output Text:
Given the influx of Southeast Asians into the United States , oxidant medications should be used with caution , especially if an infection is present , in individuals of ethnic backgrounds that have an increased prevalence of hemoglobin E . 