To me this indicates no current potential for a mass pandemic, but rather a good candidate for the antibody-based treatment being researched.

http://www.dana-farber.org/Newsroom/...y-disease.aspx
Scientists identify antibodies against deadly emerging respiratory disease
April 28, 2014
Tags: Antibody, BasicResearch

Discovery could lead to prevention and treatment of Middle East Respiratory Syndrome

...

The report in PNAS said laboratory studies of how the virus evolves in response to exposure to neutralizing antibodies suggest that the MERS virus wonít easily shape-shift to evade antibody treatments, as some viruses do. Marascoís team found that the same mutations that enabled the MERS virus to escape neutralizing antibodies also weakened the virusís ability to replicate.

Marasco added that an antibody-based treatment for MERS would be administered by injection and could provide protection for about three weeks.
Study here:

Identification of human neutralizing antibodies against MERS-CoV and their role in virus adaptive evolution