Middle East respiratory syndrome (MERS): A new zoonotic viral pneumonia

Cunha, Cheston B; Opal, Steven M

the SARS-CoV receptor, the MERS-CoV cell receptor has been identified as DDP4 (dipeptidyl peptidase 4) which interacts with the MERS-CoV surface protein. MERS-CoV is present in ciliated bronchial epithelium, in terminal bronchial epithelium, and alveolar macrophages. 5 Aside from tissue culture, MERS-CoV may be diagnosed by ELISA, IFA, or microneutralization assay (MNT). The CDC has developed a real-time reverse transcriptase (RT) PCR assay that is available worldwide to diagnose MERS. MERS-CoV is present in serum, feces, and urine but highest concentrations are in lower respiratory secretions. Previous exposure to SARS, i.e., anti-SARS-CoV antibodies appears to confer some protective immunity to MERS-CoV, i.e., less severe infections. [6] [7] [8] Epidemiology In June 2012 a novel β coronavirus (MERS-CoV) was first isolated from the respiratory tract of a fatal case of viral pneumonia in a Saudi businessman. Since that time, MERS has been reported in 20 countries. The spectrum of MERS ranges from a mild viral respiratory illness to a rapidly fatal viral pneumonia complicated by acute respiratory distress syndrome (ARDS) and acute renal failure (ARF). There have been MERS outbreaks in health facilities and clusters within families and person-to-person transmission has been demonstrated. Household and nosocomial transmission may occur as well. 9, 10 At the present time, the pandemic potential for MERS appears low. While having a high case fatality rate, the transmissibility of MERS appears to be modest. In contrast, SARS had low case fatality rate but was highly transmissible. [11] [12] [13] Pandemic influenza is feared because the viral strains causing pandemic influenza (e.g., the 1918 H1N1 strain) can possess both the ability to rapidly transmit the influenza among humans and has a high fatality rate, particularly in young healthy adults. 14,15 Among the zoonotic viral pneumonias, avian influenza (H 7 N 9 ) has a comparable high fatality rate, and a high pandemic potential since the zoonotic vectors are migratory birds. 16 Outside of the Arabian Peninsula, MERS cases have been travel-related and traceable to the Arabian Peninsula. According to the CDC, the first United States case occurred on May 2, 2014 in Indiana. This first US case was a traveler from Saudi Arabia to Indiana via London and Chicago. The patient was a healthcare worker and lived and worked in Saudi Arabia. The second case of MERS occurred in Florida on May 11, 2014 and was also imported from a traveler from Saudi Arabia. This patient was also a healthcare worker who traveled to Florida from Saudi Arabia via London, Boston, and Atlanta. The third US case had casual contact with the initial Indiana case, raising questions about person-to-person spread. The probable third US case was diagnosed on the basis of positive ELISA and IFA with a negative MNT. According to the WHO another MERS case was reported in Jordan on May 25, 2014 in a 69-y-old male. He was initially hospitalized for a surgical procedure and subsequently discharged. After 5 d he developed fever and was readmitted to the same hospital 3 d later. After 2 d in hospital, he developed a cough and chest radiograph showed pneumonia. MERS was suspected but MERS testing was negative. He remains critically ill in the ICU 10 d after the initial MERS testing. A second specimen was taken that was positive for MERS.