Table 1.

Supporting evidence of the epidemiologic pattern of MERS-CoV

Supporting evidence of epidemiologic pattern	Epidemic (human to human)	Sporadic, animal source	Sporadic, deliberate release
Low case numbers for 12 months		✓	✓
Low estimates of R0		✓	✓
Long persistence despite low R0		✓	✓
Some person-to-person transmission documented	✓	?	?
Hospital outbreaks	✓		?a
No epidemics arising from mass gatherings		✓	?
Evidence of multiple introductions in a single outbreak			✓
Several cases without an identified epidemiologic link to a human case of MERS-CoV		✓	✓
Several cases without an identified epidemiologic link to a zoonotic source		?	✓
Several cases with no link to human OR zoonotic source			✓
MERS-CoV identified in camels		✓
Multiple genetic strains in a single hospital outbreak at Al Ahsa Hospital		?b	✓
Active surveillance had not found evidence of a high proportion of undetected cases		✓	✓

^aDeliberate release inside hospitals could explain this

^bFor this to be the explanation, simultaneous animal exposure would have to have occurred to animal hosts carrying different strains in the same time frame to cause concurrent human infections from different sources