Presenting signs and symptoms may include high-grade fever, non-productive cough, dyspnea, headache, myalgia, nausea, vomiting, and diarrhea that may precede the respiratory symptoms. Most asymptomatic cases have been discovered through screening after contact with a known case. Ĭlinically, MERS-CoV causes symptoms of upper and lower RTIs. The average age of presentation is 50 years, with a male predominance. The incubation period for the presentation of MERS-CoV symptoms is 2–14 days and it remains unknown whether patients are infectious during the incubation period. The CDC defines a laboratory-confirmed case of MERS-CoV as a patient with a positive PCR from a respiratory sample, and a probable case as a patient who had close contact with a confirmed case but inconclusive laboratory evidence. Ĭase Definition and Clinical Presentation The United States Centers for Disease Control and Prevention (CDC) recommends standard contact and airborne precautions with the use of an N-95 mask when caring for an infected patient. Propensity for the MERS-CoV to replicate in the lower respiratory tract may account for the observed limited transmission. reported a similar R 0 at 0.63, but warned that in the absence of infection control measures, R 0 may range from 0.8–1.3 and could lead to a self-sustaining transmission. Using two transmission scenarios, Breban et al. The basic reproductive rate for MERS-CoV has still not been determined with certainty.

The largest cluster reported so far has been in 23 HCWs in a hospital in Al Hasa, Kingdom of Saudi Arabia (KSA), while the largest family cluster has been in three infected brothers from Riyadh, KSA. Several clusters of MERS-CoV cases have been reported, mainly among household members and health care workers (HCWs), suggesting that transmission is through close contact. MERS-CoV has been detected by reverse transcription PCR (RT-PCR) from the nasal swabs of three camels in Qatar and was linked to two confirmed human cases with high similarity upon sequencing, suggesting a possible respiratory mode of transmission. However, respiratory transmission is currently considered as the most likely route of transmission. reported the finding of MERS-CoV in camel milk in Qatar. The first reported case of MERS-CoV in Yemen occurred in a Yemeni pilot who consumed raw camel milk, and Reusken et al. Camel milk was investigated as a possible route of transmission, given the common practice of consuming camel milk in the Arabian Peninsula. The exact mode of transmission from camels to humans remains to be confirmed. Neutralizing antibodies for MERS-CoV have been detected in dromedary camels from Oman, Canary Islands, Egypt, Jordan, United Arab Emirates, and Saudi Arabia. MERS-CoV uses the DPP4 (CD26) receptor to gain entry and effectively replicate in camel cell lines. MERS-CoV appears to have been circulating in dromedary camels for over 20 years. Since human-bat contact is limited, camels have been implicated as probable intermediate hosts.

Three lines of evidence currently support this theory: (1) the very close phylogenetic similarity with the bat Betacoronaviruses: BtCoV-HKU4 and BtCoV-HKU5 (2) closely related coronavirus sequences have been recovered from bats in Africa, Asia, the Americas, and Eurasia and (3) MERS-CoV uses the evolutionary conserved dipeptidyl peptidase-4 (DPP4) protein in Pipistrellus pipistrellus bats for cell entry. MERS-CoV marks the second known zoonotic introduction of a highly pathogenic coronavirus, probably originating from bats.

SARS-CoV caused a global pandemic, with 8,400 recorded cases and 800 deaths. The first zoonotic introduction of a coronavirus into the human population occurred with the severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002. Prior to 2003, coronaviruses were not considered serious human pathogens since they only caused mild upper respiratory tract infections (URTIs). With a case fatality rate of 35%, an urgent response is needed to prevent a global pandemic. First reported in 2012, Middle East respiratory syndrome coronavirus (MERS-CoV) is a novel coronavirus and the first lineage 2C Betacoronavirus known to infect humans.

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