Updated Information on the Epidemiology of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Infection and Guidance for the Public, Clinicians, and Public Health Authorities, 2012–2013

Gayle Langley


Morbidity and Mortality Weekly Report. 2013;62(38):793-796. 

In This Article

Abstract and Introduction


The Middle East respiratory syndrome coronavirus (MERS-CoV) was first reported to cause human infection in September 2012.[1] In July 2013, the World Health Organization (WHO) International Health Regulations Emergency Committee determined that MERS-CoV did not meet criteria for a "public health emergency of international concern," but was nevertheless of "serious and great concern".[2] This report summarizes epidemiologic information and provides updates to CDC guidance about patient evaluation, case definitions, travel, and infection control as of September 20, 2013.

As of September 20, 2013, a total of 130 cases from eight countries have been reported to WHO; 58 (45%) of these cases have been fatal (Figure 1). All cases have been directly or indirectly linked through travel to or residence in four countries: Saudi Arabia, Qatar, Jordan, and the United Arab Emirates (UAE) (Figure 2). The median age of persons with confirmed MERS-CoV infection is 50 years (range: 2–94 years). The male-to-female ratio is 1.6 to 1.0. Twenty-three (18%) of the cases occurred in persons who were identified as health-care workers. Although most reported cases involved severe respiratory illness requiring hospitalization, at least 27 (21%) involved mild or no symptoms. Despite evidence of person-to-person transmission, the number of contacts infected by persons with confirmed infections appears to be limited. No cases have been reported in the United States, although 82 persons from 29 states have been tested for MERS-CoV infection.

Figure 1.

Number of cases of Middle East respiratory syndrome coronavirus infection (58 fatal and 72 nonfatal) reported to the World Health Organization (WHO) as of September 20, 2013, by month of illness onset — worldwide, 2012–2013
* Case count for May assumes that three cases included in WHO announcements on May 22, May 23, and June 2, 2013, had symptom onset during May 2013.
† Case count for June assumes that 22 cases included in WHO announcements on June 14, June 17, June 22, June 23, June 26, July 5, July 7, and July 11, 2013, had symptom onset during June 2013.
§ Case count for July assumes that 10 cases included in WHO announcements on July 18, July 21, and August 1, 2013, had symptom onset during July 2013.
¶ Case count for August assumes that 25 cases (two on August 28, one on August 29, two on August 30, and 16 on September 16) had symptom onset during August 2013.

Figure 2.

Confirmed cases of Middle East respiratory syndrome coronavirus infection (N = 130) reported to the World Health Organization as of September 20, 2013, and history of travel from in or near the Arabian Peninsula* within 14 days of illness onset — worldwide, 2012–2013
* Dots are not geographically representative of exact location of residences of persons with infection.

Potential animal reservoirs and mechanism(s) of transmission of MERS-CoV to humans remain unclear. A zoonotic origin for MERS-CoV was initially suggested by high genetic similarity to bat coronaviruses,[3] and some recent reports have described serologic data from camels and the identification of related viruses in bats.[4–6] However, more epidemiologic data linking cases to infected animals are needed to determine if a particular species is a host, a source of human infection, or both.

To date, the largest, most complete clinical case series published included 47 patients; most had fever (98%), cough (83%), and shortness of breath (72%). Many also had gastrointestinal symptoms (26% had diarrhea, and 21% had vomiting). All but two patients (96%) had one or more chronic medical conditions, including diabetes (68%), hypertension (34%), heart disease (28%), and kidney disease (49%). Thirty-four (72%) had more than one chronic condition.[7] Nearly half the patients in this series were part of a health-care–associated outbreak in Al-Ahsa, Saudi Arabia (i.e., a population that would be expected to have high rates of underlying conditions).[8] Also, the prevalence of diabetes in persons aged ≥50 years in Saudi Arabia has been reported to be nearly 63%.[9] It remains unclear whether persons with specific conditions are disproportionately infected with MERS-CoV or have more severe disease.