Estimates of the risk of large or long-lasting outbreaks of Middle East respiratory syndrome after importations outside the Arabian Peninsula

• MERS outbreak clusters outside the Arabian Peninsula ranged in size from 1 to 186.
• Cluster data show declining transmission rate in later transmission generations.
• Model projects tempered risk of large, long-lasting outbreaks after importations.
• Explosive outbreaks are possible, but control measures are likely to be effective.

We quantify outbreak risk after importations of Middle East respiratory syndrome outside the Arabian Peninsula. Data from 31 importation events show strong statistical support for lower transmissibility after early transmission generations. Our model projects the risk of ≥10, 100, and 500 transmissions as 11%, 2%, and 0.02%, and ≥1, 2, 3, and 4 generations as 23%, 14%, 0.9%, and 0.05%, respectively. Our results suggest tempered risk of large, long-lasting outbreaks with appropriate control measures.