Between 8 and 14 September 2016, the cities of Jeddah, Makkah, and Madinah, Kingdom of Saudi Arabia (KSA), hosted the annual Hajj pilgrimage [
3]. An estimated 2 million pilgrims attended from 184 countries, lived in crowded conditions, and performed religious rites in close proximity, exposing themselves and the local Saudi population to a range of infectious diseases. MERS-CoV was first isolated and identified in a 68-year-old patient who died of pneumonia and multi-organ failure in Jeddah, KSA, in June 2012 [
9]. This is the second time (after severe acute respiratory syndrome coronavirus, SARS-CoV) [
10] in the 21st century that a coronavirus has emerged as a new lethal zoonotic pathogen of humans.
Serological studies show that camels have been infected with MERS-CoV for 20 years. MERS-CoV is a common infection in dromedary camels, and there is accumulating evidence that the sporadic human outbreaks are seeded by zoonotic infection from camels [
11]. There have been intermittent MERS-CoV community cases [
12] and hospital outbreaks [
13‐
16], but no sustained epidemic [
7]. Hospital case clusters of MERS-CoV represent the primary location where rapid human-to-human transmission of MERS-CoV have occurred; although limited spread among family members has been observed [
17,
18]. SARS-CoV [
10] was also predominantly spread through nosocomial transmission, but the epidemiological features of MERS-CoV remain less clear [
19]. While 90 % of reported MERS-CoV cases have been from KSA, MERS-CoV has spread to 27 countries in Europe, North Africa, Asia, USA, and the Middle East. All cases had travel links with KSA or other countries in the Arabian Peninsula. As of 26 August 2016, 1,800 confirmed MERS-CoV cases have been reported to WHO from over 21 countries, including 640 deaths (35 % case fatality rate). MERS-CoV-related mortality is significantly increased in patients with comorbidities such as diabetes, renal disease, cardiac disease, lung and liver disease, or other immunosuppressive conditions [
7,
20]. There are no known effective treatments or preventive vaccines for MERS-CoV [
21].