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CDPH Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Information Webpage 


MERS is caused by a distinctive coronavirus (MERSCoV). Typical early symptoms include fever, cough, chills, and shortness of breath. Pneumonia is common. Some cases have had diarrhea, nausea, or vomiting. Other cases tested after their contact with MERS patients have had no symptoms. Complications of MERS include severe pneumonia and organ failure. As of June 2015, approximately 35-40% of confirmed cases have died. Most severe cases of MERS have had underlying chronic medical conditions. There is no known vaccine or specific treatment; management is supportive.

The majority of MERS cases have resulted from human-to-human transmission in health care settings. The virus does not seem to pass easily from person to person unless there is close contact, such as occurs when providing unprotected care to a patient. Dromedary camels are a host for MERS-CoV, but their roles in transmission is unclear.

Since the first case of MERS was reported in 2012 from Saudi Arabia, more than 1200 confirmed cases of MERS have been reported in 25 countries. All MERS cases to date have resided in or traveled to the Arabian Peninsula or have been linked to a case who had recently traveled there. The only two cases of MERS to date in the United States (Indiana and Florida), both healthcare workers exposed while working in Saudi Arabia, were reported in May 2014.

Since 2013, more than 60 persons have been investigated in California for possible infection with the MERS coronavirus. All have tested negative; the risk of MERS in California has been very low. No travel warnings or restrictions have been issued related to MERS-CoV.

A large, ongoing outbreak in South Korea associated with healthcare facilities began when an employee of an agricultural products company returned from the Arabian Peninsula in May 2015. More than 125 cases, mostly patients, staff and visitors at health care facilities in or nearby Seoul, have been reported by the South Korean Ministry of Health as of June 2015.

Patients Under Investigation

A person with the following characteristics should be considered a patient under investigation (PUI):


Clinical:    Fever AND

               Pneumonia or acute respiratory distress syndrome (based on clinical or radiologic evidence)


  • History of travel from countries in or near the Arabian Peninsula* 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
  • Addition related to the 2015 outbreak: History of being in a healthcare 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 healthcare 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 healthcare-associated cases of MERS have been identified


C.        EITHER Fever OR Symptoms of respiratory illness (not necessarily pneumonia; e.g., cough, shortness of breath)


Close contact* with a confirmed MERS case while the case was ill.


*A close contact is defined as any person who has been:

  • Within approximately 6 feet (2 meters) or within the room or care area for a prolonged period of time (e.g., healthcare personnel, household members) while not wearing recommended personal protective equipment (i.e., gowns, gloves, respirator, eye protection); OR
  • In direct contact with infectious secretions (e.g., being coughed on) while not wearing recommended personal protective equipment (i.e., gowns, gloves, respirator, eye protection).

   At this time, brief interactions, such as walking by a person, are considered low risk and do not constitute close contact.

**Countries in or near the Arabian Peninsula include Bahrain, Iraq, Iran, Israel, Jordan, Kuwait, Lebanon, Oman, Palestinian territories, Qatar, Saudi Arabia, Syria, the United Arab Emirates (UAE), and Yemen.

Infection Control Guidance for MERS-CoV Infection

CDC is recommending that infection control guidance developed for SARS be implemented for patients with known or suspected MERS-CoV infection. Therefore, Airborne and Contact Precautions, in addition to Standard Precautions, should be applied when caring for patients with known of possible MERS-CoV infection. CDC interim infection prevention and control guidance for hospitalized patients with MERS-CoV is available at: http://www.cdc.gov/coronavirus/mers/infection-prevention-control.html. CDC infection control guidance for SARS is available at: http://www.cdc.gov/sars/infection/.

General Information
Information for Health Professionals
General Guidelines for Preventing Transmission
Infection Control
Last modified on: 6/15/2015 11:16 AM