Hi,
the ClassBridge is not only called at initial indexing, but also when the entity updates, however due to a bug in Hibernate Core collection changes would not trigger a update event. See
http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-56. This got fixed in release 3.0.1.GA. The question is - which version of Search are you using?
Regarding the ClassBridge approach. I reckon a FieldBridge would do as well, provided you annotate the getters. You could add a property
hasDesease and a matching getter. Mark the getter as @Transient and place a @Field on it. In the getter you just return
!deseaseList.isEmpty(). I think that should work.
--Hardy