In the sentence extracted from biomedical literature, identify all the disease entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="disease"> to denote a disease.

### Input Text: The spectrum comprises 15 % large deletions , 26 % small length alterations , and 42 % base substitutions .
### Output Text:
The spectrum comprises 15 % large deletions , 26 % small length alterations , and 42 % base substitutions . 