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: The incidence of severe adenovirus disease in pediatrics is increasing in association with growing numbers of immunocompromised children , where case fatality rates as high as 50 % to 80 % have been reported .
### Output Text:
The incidence of severe adenovirus disease in pediatrics is increasing in association with growing numbers of immunocompromised children , where case fatality rates as high as 50 % to 80 % have been reported . 