By Stan Deresinski, MD, FACP, FIDSA

Dr. Deresinski is Clinical Professor of Medicine, Stanford University.

Dr. Deresinski reports that he has served as a one-time consultant for Cubist and Bayer.

On May 20, 2015, a 68-year-old Korean man with fever and cough who had returned eight days previously from a trip to Saudi Arabia and the United Arab Emirates was found to be infected with Middle East Respiratory Syndrome (MERS) coronavirus. The patient, unfortunately, had visited three different clinics before being admitted to St. Mary’s hospital in Pyeongtaek, South Korea. While hospitalized, he shared a room with another patient, who, as a consequence, contracted MERS. Additional cases occurred and, after 29 of the first 36 were found to have been contracted at the Pyeongtaek hospital, the hospital was closed and its staff was quarantined.1 Cases nonetheless continued to occur elsewhere, with most being acquired in health care facilities. Eventually, a second facility, Medi Heal hospital in Seoul, was closed. As of June 12, South Korea had recorded 126 cases and 14 deaths from MERS.The median age of the patients was 56 years old (16 to 84 years) and the majority were men (59%). Ten (7.9%) are health care professionals.

All cases to date have been linked to a single chain of transmission and, except for the index case, were associated with health care facilities. An investigation identified 44 hospitals at which either transmission had occurred or a confirmed case of MERS had visited prior to their diagnostic confirmation.2,3 The transmission chain has included at least one fourth-generation case — an ambulance driver who had transported a third-generation case to a hospital. As of June 12, 3680 contacts have been identified. Globally, since September 2012, the World Health Organization (WHO) has been notified of 1289 laboratory-confirmed cases of infection with MERS-CoV, including at least 455 related deaths.

MERS was first identified in 2012 in Saudi Arabia. Including the outbreak in South Korea, MERS has infected nearly 1200 people and led to 442 deaths.

Human cases have recently been reported in Oman, Qatar, Saudi Arabia, and the United Arab Emirates, as well as an imported case in Germany. Strains of the virus that are identical to human strains have been isolated from dromedary camels in several countries, including Egypt, Oman, Qatar, and Saudi Arabia. While transmission of MERS in healthcare facilities in the Middle East occurs, the experience in South Korea has been extraordinary. Genomic sequencing of a limited number of viruses indicates that the Korean virus is most closely related to a virus detected in 2015 in Saudi Arabia. Preliminary analysis has failed to find evidence that the transmissibility of the virus has increased.

The Korean experience has increased the level of concern about the importation of cases into the United States, where the >CDC has recommended the following criteria for deciding which patients should be evaluated for MERS:4

A. Fever AND pneumonia or acute respiratory distress syndrome (based on clinical or radiologic evidence) AND EITHER:

  • a history of travel from countries in or near the Arabian Peninsula1 within 14 days before symptom onset; OR
  • close contact with a symptomatic traveler who developed fever and acute respiratory illness (not necessarily pneumonia) within 14 days after traveling from countries in or near the Arabian Peninsula; OR
  • a history of being in a health care facility (as a patient, worker, or visitor) in the Republic of Korea within 14 days before symptom onset; OR
  • a member of a cluster of patients with severe acute respiratory illness (e.g., fever and pneumonia requiring hospitalization) of unknown etiology in which MERS-CoV is being evaluated, in consultation with state and local health departments;


B. Fever AND symptoms of respiratory illness (not necessarily pneumonia; e.g., cough, shortness of breath) AND being in a health care facility (as a patient, worker, or visitor) within 14 days before symptom onset in a country or territory in or near the Arabian Peninsula in which recent health care-associated cases of MERS have been identified.


C. Fever OR symptoms of respiratory illness (not necessarily pneumonia; e.g., cough, shortness of breath) AND close contact with a confirmed MERS case while the case was ill.

The Korean experience illustrates the critical importance of early recognition of potential MERS cases and rapid implementation of strict infection control measures.


  1. Dyer O. South Korea scrambles to contain MERS virus. BMJ 2015;350:h3095.
  2. Global Alert and Response. Middle East respiratory syndrome coronavirus (MERS-CoV) — Republic of Korea.
  3. WHO. Fact sheet on Middle East respiratory syndrome coronavirus. WHO Weekly Epidemiological Record. 12 June 2015.
  4. CDC. Middle East Respiratory Syndrome (MERS). Interim Guidance for Healthcare Professionals.