Chapter 3 - Middle Eastern respiratory syndrome

ABSTRACT

Middle East respiratory virus syndrome (MERS) is a viral disease that primarily affects the respiratory system, but also has a major impact on the kidneys and nervous system and, to a lesser extent, on the intestines, liver, and heart. Over 2500 cases and 850 deaths have been confirmed as of 2019. The fatality rate is approximately 35%, more than that caused by severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2 (that causes COVID-19). The first known case of MERS in humans was reported in 2012 in Saudi Arabia but the virus was present in stored serum samples from dromedary (one-humped) camels from Africa and the Middle East for decades before that time. Since then, it spread to at least 27 countries around the world, most of which are related to travel to the Arabian Peninsula. The coronavirus that causes MERS, MERS-CoV, is related to several other human coronaviruses that typically cause cold-like illness as well as to SARS-CoV and SARS-CoV-2. MERS-CoV is from the subgenus Merbecovirus, while SARS-CoV and SARS-CoV-2 are in Sarbecovirus. MERS-CoV also uses dipeptidyl peptidase 4 as its host cell receptor, while SARS-CoV and SARS-CoV-2 use angiotensin-converting enzyme 2. While MERS-CoV is transmittable between people in close contact with an infected person, many infections are zoonotic and are due to inhaling infectious respiratory droplets from dromedaries or consuming their raw milk or urine. Many cases are nosocomial (acquired in healthcare facilities). Fortunately, MERS-CoV only can pass through several rounds of human-to-human transmission, unlike SARS-CoV-2. Much of the pathology is due to an excessive inflammatory type of immune response caused by cytokines and chemokines, abnormal blood coagulation, and virus-induced apoptosis (programmed cell death). Bats appear to be the reservoir hosts and should be monitored for possible zoonotic transmission outside of the Middle East, in line with the One Health approach.