Middle East Respiratory Syndrome Virus Pathogenesis.

Coronaviruses (CoVs) are enveloped RNA viruses that infect birds, mammals, and humans. Infections caused by human coronaviruses (hCoVs) are mostly associated with the respiratory, enteric, and nervous systems. The hCoVs only occasionally induce lower respiratory tract disease, including bronchitis, bronchiolitis, and pneumonia. In 2002 to 2003, a global outbreak of severe acute respiratory syndrome (SARS) was the seminal detection of a novel CoV (SARS-CoV). A decade later (June 2012), another novel CoV was implicated as the cause of Middle East respiratory syndrome (MERS) in Saudi Arabia. Although bats might serve as a reservoir of MERS-CoV, it is unlikely that they are the direct source for most human cases. Severe lines of evidence suggest that dromedary camels have been the major cause of transmission to humans. The emergence of MERS-CoV has triggered serious concerns about the potential for a widespread outbreak. All MERS cases were linked directly or indirectly to the Middle East region including Saudi Arabia, Jordan, Qatar, Oman, Kuwait, and UAE. MERS cases have also been reported in the later phases in the United Kingdom, France, Germany, Italy, Spain, and Tunisia. Most of these MERS cases were linked with the Middle East. The high mortality rates in family-based and hospital-based outbreaks were reported among patients with comorbidities such as diabetes and renal failure. MERS-CoV causes an acute, highly lethal pneumonia and renal dysfunction. The major complications reported in fatal cases are hyperkalemia with associated ventricular tachycardia, disseminated intravascular coagulation, pericarditis, and multiorgan failure. The case-fatality rate seems to be higher for MERS-CoV (around 30%) than for SARS-CoV (9.6%). The combination regimen of type 1 interferon + lopinavir/ritonavir is considered as the first-line therapy for MERS. Antiviral treatment is generally recommended for 10 to 14 days in patients with MERS-CoV infection. Convalescent plasma therapy has shown some efficacy among patients refractory to antiviral drugs if administered within 2 weeks of the onset of the disease.