10:00 Dose of EIDology: What is an 'Emerging Infectious Disease?'

...And Where do They 'Emerge' From?  

An emerging infectious disease ('EID') is a disease with a microbial cause that is new to a given population.  A disease can be considered "emerging" if it has never before been seen in humans (such as MERS), or it can be considered emerging if it is new to a geographic area (such as West Nile encephalitis in the US over the last decade).  Finally, a disease can be considered "re-emerging" if it was well controlled for many years, but has resurged (such as tuberculosis in Western countries).

Altered geographic distributions are often related to social factors affecting global interconnectedness.  Re-emerging diseases are often related to lapsed control measures (such as vaccination rates) or loss of effectiveness of control measures (such as those giving rise to multi-drug resistant tuberculosis).  Completely new emerging diseases, from AIDS to EBOLA to MERS, do frequently have a commonality: they are introduced into humans from animals.  What are the principles behind that, and how does it work?  That's a 5:00 thing!