Micro140 is an infectious disease case scenario discussion virtual club meeting at 5pm New York time (usually 10pm UK time - see e.g. World Clock for confirmation).
It is held on Twitter, open to anybody, using the "hashtag" #micro140. Tweetchat is a good way to participate. The convener of the club is Dr Nick Bennett, author of the "Correcting the AIDS Lies" and Culture and Sensitivity blogs, who tweets as @peds_id_doc.