Is there a common data base or a platform for doctors to talk, search and share medical events and sicknesses worldwide?

Good question: Most of the best data bases of information are set up by the different societies. The databases of information are linked to the literature. Thus, there may be a short description of a particular topic with references that link to pubmed. As far as a forum for questions, there are chat rooms or interactive live web discussions for particular topics and exchange of ideas.