Middle East respiratory syndrome (MERS) is a viral respiratory infection caused by Middle East respiratory syndrome–related coronavirus (MERS-CoV). Symptoms may range from none, to mild, to severe depending on age and risk level. Typical symptoms include fever, cough, diarrhea, and shortness of breath. The disease is typically more severe in those with other health problems. The first case was identified in June 2012 by Egyptian physician Ali Mohamed Zaki at the Dr. Soliman Fakeeh Hospital in Jeddah, Saudi Arabia, and most cases have occurred in the Arabian Peninsula. Over 2,600 cases have been reported as of January 2021, including 45 cases in the year 2020. About 35% of those who are diagnosed with the disease die from it. Larger outbreaks have occurred in South Korea in 2015 and in Saudi Arabia in 2018. MERS-CoV is a virus in the coronavirus family believed to be originally from bats. However, humans are typically infected from camels, either during direct contact or indirectly through respiratory droplets. Spread between humans typically requires close contact with an infected person. Its spread is uncommon outside of hospitals. Thus, its risk to the global population is currently deemed to be significantly low. Diagnosis is by rRT-PCR testing of blood and respiratory samples. There is no specific vaccine or treatment for the disease, but a number are being developed. The World Health Organization (WHO) recommends that those who come in contact with camels wash their hands and not touch sick camels. They also recommend that camel-based food products be appropriately cooked. Treatments that help with the symptoms and support body functioning may be used. Previous infection with MERS can confer cross-reactive immunity to SARS-CoV-2 and provide partial protection against COVID-19. However, co-infection with SARS-CoV-2 and MERS-CoV is possible and could lead to a recombination event.
Signs and symptoms
Early reports compared the viruses to severe acute respiratory syndrome (SARS), and it has been referred to as Saudi Arabia's SARS-like virus. The first person, in June 2012, had a fever, cough, expectoration, and shortness of breath. One review of 47 laboratory confirmed cases in Saudi Arabia gave the most common presenting symptoms as fever in 98%, cough in 83%, shortness of breath in 72% and myalgia in 32% of people. There were also frequent gastrointestinal symptoms with diarrhea in 26%, vomiting in 21%, abdominal pain in 17% of people. 72% of people required mechanical ventilation. There were also 3.3 males for every female. One study of a hospital-based outbreak of MERS had an estimated incubation period of 5.5 days (95% confidence interval 1.9 to 14.7 days). MERS can range from asymptomatic disease to severe pneumonia leading to acute respiratory distress syndrome (ARDS). Kidney failure, disseminated intravascular coagulation (DIC), and pericarditis have also been reported.
Cause
Virology
Middle East respiratory syndrome is caused by the MERS coronavirus (MERS-CoV), a species with single-stranded RNA belonging to the genus betacoronavirus which is distinct from SARS coronavirus and the common-cold coronavirus. Its genomes are phylogenetically classified into two clades, Clades A and B. Early cases of MERS were of Clade A clusters (EMC/2012 and Jordan-N3/2012), while new cases are genetically different in general (Clade B). The virus grows readily on Vero cells and LLC-MK2 cells. In November 2012, Egyptian virologist Dr. Ali Zaki sent a virus sample from the first confirmed case in Saudi Arabia to virologist Ron Fouchier, a leading coronavirus researcher at the Erasmus Medical Center (EMC) in Rotterdam, the Netherlands. The second laboratory-proven case was in London, confirmed by the UK Health Protection Agency (HPA). The HPA named the virus the London1_novel CoV 2012.
Transmission
Camels A study performed between 2010 and 2013, in which the incidence of MERS was evaluated in 310 dromedary camels, revealed high titers of neutralizing antibodies to MERS-CoV in the blood serum of these animals. A further study sequenced MERS-CoV from nasal swabs of dromedary camels in Saudi Arabia and found they had sequences identical to previously sequenced human isolates. Some individual camels were also found to have more than one genomic variant in their nasopharynx. There is also a 2014 report of a Saudi Arabian man who became ill seven days after applying topical medicine to the noses of several sick camels and later he and one of the camels were found to have identical strains of MERS-CoV. It is still unclear how the virus is transmitted from camels to humans. In 2014, the Saudi Ministry of Agriculture advised people to avoid contact with camels or wear breathing masks when around them. In response "some people have refused to listen to the government's advice" and kiss their camels in defiance of their government's advice. In 2020, the World Health Organization advised avoiding contact with camels and to eat only fully cooked camel meat, pasteurized camel milk, and to avoid drinking camel urine.
Between people There has been evidence of limited, but not sustained spread of MERS-CoV from person to person, both in households as well as in health care settings like hospitals. Most transmission has occurred "in the circumstances of close contact with severely ill persons in healthcare or household settings" and there is no evidence of transmission from asymptomatic cases. Cluster sizes have ranged from 1 to 26 people, with an average of 2.7.
Diagnosis According to World Health Organization, the interim case definition is that a confirmed case is identified in a person with a positive lab test by "molecular diagnostics including either a positive polymerase chain reaction (PCR) on at least two specific genomic targets or a single positive target with sequencing on a second".
World Health Organization According to the WHO, a probable case is:
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