The Infectious Disease Ontology is available in both OBO-Edit and Protege-OWL formats.  Current versions are available for download and by svn through the IDO Google Code site here.

Previous Versions:

The OWL version released on May 20, 2010 is available here.

The OWL version released on August 14, 2009 is available here.

OBO-Edit

Protege

The core Infectious Disease Ontology is an ontology of entities generally relevant to both the biomedical and clinical aspects of infectious diseases, such as ‘pathogen’, ‘host’, ‘vector’, and ‘vaccine’.  The structure of IDO adheres to the Basic Formal Ontology.  Terms in IDO that are within the scope of other OBO Foundry ontologies, such as the Gene Ontology, are derived from those ontologies.  Other terms are defined as cross-products of terms from Foundry ontologies, to the extent possible.

Information on the IDO extension ontologies can be found here.