Epidemiology

The first case of MERS was reported in a 60-year-old man in Jeddah, Saudi Arabia in 2012.[14] The patient died from severe pneumonia and multi-organ failure. Since then, many cases and clusters have been reported with the majority of infections acquired in the Arabian Peninsula and its surrounding countries, most commonly Saudi Arabia, the United Arab Emirates (UAE), Oman, Qatar, and Jordan.

Cases associated with travel from these countries have been limited to small clusters of a few individuals,[15][16][17][18] except for one large outbreak of 186 reported cases in the Republic of Korea (South Korea) in 2015,[19][20][21] and one superspreader event in Riyadh (Saudi Arabia) in 2017 where 44 cases were linked to one patient who presented with acute renal failure.[11]Two cases were reported in the US in 2014, both in travellers from Saudi Arabia.[22] There have been no cases reported in the US since. Five laboratory-confirmed cases have been reported in the UK since 2012, with the latest reported in August 2018.[23] Other countries with travel-associated cases include France, Italy, Greece, Turkey, Lebanon, Germany, Austria, Netherlands, China, Malaysia, Thailand, Philippines, and Egypt. A case was reported in the Republic of Korea in September 2018 in a Korean national who visited Kuwait and returned to Korea via Dubai. Twenty-one contacts are currently under active surveillance.[24]

As of the end of August 2018, 2248 laboratory-confirmed cases, including 798 deaths (35.5% case fatality rate), were reported globally since 2012 across 27 countries. The majority of these cases were reported from Saudi Arabia (1871 cases). The 50-59 years age group is at highest risk for acquiring primary infection.[25]

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Ninety-eight percent of cases have been reported in adults (defined as age >14 years).[8] Although infection has been reported in different age groups within the adult population, the median age of patients ranges from 50 to 67 years of age.[4][9][26] Age ≥50 years is associated with a higher risk of mortality.[5][27] In one cohort study, mortality increased with increasing age to reach 75% in patients >60 years of age.[8] The majority of cases occur in males.[25] Infection in children is rare, although the reason for this is unknown.[12][13]

The majority of cases are a result of human-to-human transmission rather than camel-to-human transmission, with peaks of confirmed cases occurring during nosocomial outbreaks.[6][7][28] Transmission has been well documented in family clusters.[18][29][30] However, it has been reported more commonly in nosocomial outbreaks (e.g., haemodialysis units, intensive care units, medical wards).[6][7][30][31][32][33][34]

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