Fig. 4

A speculative series of how humans and DCs contribute to the global tally of MERS cases. a. Risks for acquiring MERS-CoV from a DC. This illustration highlights risks that may originate from a droplet transmission component (be they larger, heavier wet droplets or the drier, airborne gel-like droplet nuclei) or a direct contact component (within the green circle). No routes of MERS-CoV acquisition to or between humans have been proven to date. Modified and reprinted from Mackay IM, Arden KE. Middle East respiratory syndrome: An emerging coronavirus infection tracked by the crowd. Virus Res 2015 Vol 202:60–88 with permission from Elsevier [5]. b Camel-to-human infections appear to be infrequent, while human-to-human spread of infection is regularly facilitated by poor IPC in healthcare settings where transmission is amplified, accounting for the bulk of cases. There are human MERS cases that do not fall into either category of source and it is unclear if these acquired infection through some entirely separate route, or from cases that escaped diagnosis. c Hypothetical ways in which subclinical (when infection may not meet a previously defined clinical threshold of signs and/or symptoms) or asymptomatic (no obvious signs or measured, noticed or recalled symptoms of illness) MERS-CoV infection may be implicated in transmission