Wednesday, January 20, 2016

The Geography of MERS

Since 2012, the World Health Organization (WHO) has been notified of 1626 laboratory-confirmed cases of Middle East Respiratory Virus Syndrome (MERS) as of January 7, 2016 (link). These cases have been reported from 26 countries as shown on the map and table below. Cases have been reported from most continents: North America, Africa, Europe, and Asia. No cases have been yet been reported from South America, Australia, or the sparsely inhabited Antarctica. More than 75% of these cases have been reported from Saudi Arabia. 

Countries Reporting MERS infections to WHO
Worldwide count of MERS cases  

The earliest cases of MERS in 2012 were geographically associated with countries in the Middle East. Numerous cases in Saudi Arabia are reported as “primary cases”, autochthonous cases, which have been infected from local animal hosts. Current research indicates that camel populations on the Arabian Peninsula are a reservoir for this coronavirus, although there may be other intermediate animal hosts as well. 

The map above only shows countries that have officially reported MERS cases to WHO, not the countries where the individual cases were initially infected. A review of the published case reports indicates local infections from animal sources has only occurred in countries on or adjacent to the Arabian Peninsula as shown in the map below. Although the MERS jump from animals to human appears to be occurring only in a small geographic region in the Middle East, this coronavirus is very infectious. Many infections on the Arabian Peninsula and elsewhere are reported to have occurred from human-to-human contact or by transmission within a healthcare facility. 

Secondary cases of infections have occurred in health care facilities in Saudi Arabia, South Korea, and other countries. The large number of MERS infections among healthcare workers, healthcare facility patients, and patient visitors is a strong indication of the infectious nature of this coronavirus. According to published information, at least 240 reported MERS cases were healthcare workers.

Last year in South Korea, 185 cases of MERS were sparked by a single infected individual who traveled to South Korea from the Middle East. The infections spread primarily though hospitals. The nature of infectious transmission in health care settings is not clear. Human-to-human airborne transmission has been proposed for pneumonia-infected “superspreaders” in South Korea (link), but human-to- fomite-to-human transmission seems to occur frequently as well. 

Because of the nature of international travel and the infectious nature of this coronavirus MERS, cases have been reported from 26 countries around the world in less than four years. We can expect more MERS cases to be infected in the Middle East and to be reported from more countries in the future. 

Countries on the Arabian Peninsula reporting autochthonous cases of MERS 

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