Middle East Respiratory Syndrome Coronavirus (MERS-CoV)

Jaffar A. Al-Tawfiq, M.D., Paul G. Auwaerter, M.D.

PATHOGENS

MERS-CoV is a coronavirus, that was described initially upon isolatation in 2012.
- β-coronavirus: not the same virus as SARS, and SARS-CoV-2 but related.
- Similar to other coronavirus described in bats.
- MERS-CoV: dromedary camels established as a host; positive specimens are known dating at least to the early 1990s.
  - Also seen in bats
Believed to be primarily a respiratory pathogen in humans, coronaviruses, as a group, cause disease ranging from the common cold to severe pulmonary illnesses

CLINICAL

All cases (WHO-reported cases = 2,626, as of May 2025), with most cases being in or near the Arabian Peninsula.
- Countries in the Arabian Peninsula with confirmed cases: Saudi Arabia, United Arab Emirates (UAE), Qatar, Oman, Jordan, Kuwait, Iran, Egypt, Yemen, Lebanon.
  - Countries with travel-related cases (imported): U.S. (2 cases), UK, France, Tunisia, Italy, Malaysia, South Korea (also indigenous transmission), Germany, Netherlands, Greece, Turkey, Austria, China, Philippines, Thailand, Algeria.
    - No reported U.S. MERS cases since 2014
  - Most cases were reported as follows: Saudi Arabia (n=2200); Republic of Korea (n=186); UAE (n=94); Jordan (n=28); and Oman (n=26)
  - Current data do not indicate a decrease in MERS-CoV prevalence among camels.
    - Human MERS cases continue to occur even in the absence of documented camel exposure.
  - Human-human spread, likely requiring close contact; nosocomially acquired cases reflect inadequate infection control practices, overcrowding and failure to recognize.
    - The majority of cases are men (69%) with a mean age of 52.4 years; 37% are aged ≥60 years, a high-risk group.
    - Place of exposure: healthcare setting (n=895); community (n=576); household (n=227); not reported (n=923).
    - Asymptomatic infections: There were 176 asymptomatic infections compared to 2,200 symptomatic cases; however, 273 of the cases did not have an assigned clinical presentation.
Symptoms: nonspecific: fever, cough and dyspnea.
- The clinical picture is variable.
  - Most fatalities have been described in hospitalized patients with comorbidities.
    - The reported MERS-CoV case fatality rate (CFR) is about 36% among lab-confirmed cases.
  - Spectrum of illness: ranges from asymptomatic or mildly symptomatic to severe cases requiring hospitalization, and may develop multiorgan failure.
- Gastrointestinal symptoms: diarrhea, vomiting and abdominal pain (up to 30%).
Consider placing patient(s) under investigation: guidance from the CDC[23].
- An acute respiratory infection, which may include fever (≥ 38°C, 100.4°F) and cough; AND
- Suspicion of pulmonary parenchymal disease (e.g., pneumonia or acute respiratory distress syndrome based on clinical or radiological evidence of consolidation) AND
  - History of travel from the Arabian Peninsula (or neighbors) within 14 days AND
  - No explanation by another infection or etiology, including all clinically indicated tests for community-acquired pneumonia
- Also, the following people may be considered for evaluation:
  - People who develop severe acute lower respiratory illness of known etiology within 14 days after travel from the Arabian Peninsula or neighboring countries but do not respond to appropriate therapy; OR
  - People who develop severe acute lower respiratory illness who are close contacts of a symptomatic traveler who developed fever and acute respiratory illness within 14 days after travel from the Arabian Peninsula or neighboring countries.

DIAGNOSIS

Laboratory: Molecular diagnostics are the method of choice for MERS-CoV.
- Real-time reverse transcription-PCR assay:
  - May test respiratory, blood and stool specimens.
    - Lower respiratory samples yield better results than upper respiratory samples.
  - Two to three nasopharyngeal samples yield the highest number of positive results.
    - Available through U.S. state health departments.
- Serology: developed, but not yet widely used for clinical care or diagnosis.
- Viral culture: should only be performed in specialized laboratories.
Additional details regarding updated information and evaluation from the CDC.

TREATMENT

General

Potential cases should be reported immediately to the local and/or state health department.
Antiviral therapy: No large clinical trials have been performed[6].
- Randomized Controlled Trial 1
  - Groups: Treatment (N = 32) vs. Placebo (N = 38)
  - Intervention:Lopinavir/Ritonavir 100 mg PO q12h + INF-β1b 0.25 mg/ml SQ on alternate days for 14 days
  - 90-day mortality:
    - Intervention group: 31.3%
    - Placebo group: 52.6%
    - Relative Risk (RR): 0.59
    - 95% Confidence Interval (CI): 0.33–1.08
    - p-value: 0.09 (not statistically significant)
- Randomized Controlled Trial 2[8]
  - Groups: Treatment (N = 43) vs. Placebo (N = 52)
  - Intervention:Lopinavir/Ritonavir 100 mg PO q12h + INF-β1b 0.25 mg/ml SQ on alternate days for 14 days
  - 90-day mortality:
    - Risk Difference: −19 percentage points
    - Upper boundary of 97.5% CI: −3
    - One-sided p-value: 0.024 (statistically significant)
- Convalescent serum with a high neutralizing antibody titer against MERS-CoV may be of use: limited data.
- There is no consensus on the optimal therapy for MERS-CoV.
Supportive care is advised, including mechanical ventilation.

Special Considerations

All contacts of potential or confirmed MERS-CoV-infected patients should be monitored for the development of respiratory symptoms.
- There is no consensus on the frequency and number of samples for testing contacts.
Infection control:
- Patients should be placed in an airborne infection isolation (AII) room (negative pressure); if unavailable, consider a transfer of the patient to a facility that has capabilities.
- Personal protection equipment (N95 masks) and environmental cleaning.
- Additional details: https://www.cdc.gov/mers/hcp/infection-control/

Prevention

Given the lack of therapeutics or vaccines to date, prevention is critical, as MERS-CoV appears to be endemic with ongoing cases.
No specific travel recommendations currently (as of July 2025).
- Travelers to Hajj: Consider protection against respiratory illness and avoid contact with individuals who are ill with respiratory infections.
- Ill travelers from the Arabian Peninsula should be reported to the CDC: https://www.cdc.gov/port-health/php/airline-guidance/preventing-spread-of-...
Respiratory prevention (general)
- Hand washing: soap and water for 20 seconds. If soap and water are unavailable, use an alcohol-based sanitizer.
- Avoid touching your face with unwashed hands.
- Avoid close contact such as kissing, sharing cups, or sharing eating utensils with sick people.
- Clean and disinfect frequently touched surfaces, such as toys and doorknobs.
- Practice cough etiquette.
See the infection control section above.

FOLLOW UP

Mortality is 36% in cases reported to the WHO.
- High rates are seen mainly in older patients and those with comorbidities.
  - Death is usually due to multiorgan failure.
  - Higher mortality in those requiring ICU admission.

OTHER INFORMATION

Appears to be a SARS-like illness, but with reduced efficacy, causing human-to-human transmission.
For the most up-to-date information, visit the following websites:
- United States/Centers for Disease Control and Prevention: http://www.cdc.gov/coronavirus/mers/index.html
- World Health Organization: https://www.who.int/health-topics/middle-east-respiratory-syndrome-coronav...

PATHOGEN SPECIFIC THERAPY

Limited data from randomized clinical trials (see therapy above)

Basis for recommendation

Bialek SR, Allen D, Alvarado-Ramy F, et al. First confirmed cases of Middle East respiratory syndrome coronavirus (MERS-CoV) infection in the United States, updated information on the epidemiology of MERS-CoV infection, and guidance for the public, clinicians, and public health authorities - May 2014. MMWR Morb Mortal Wkly Rep. 2014;63(19):431-6. [PMID:24827411]
Comment: Report of the first two cases of imported MERS-CoV into the US. This report also summarizes current recommendations regarding case description and patient evaluation, specimen procurement, and testing.
Centers for Disease Control and Prevention; Coronavirus--Middle East Respiratory Syndrome (MERS); http://www.cdc.gov/coronavirus/mers (accessed 6/14/25, last updated 12/4/24))Guidance from the CDC: Visit the URL for the most up-to-date information.Only two cases have been described as diagnosed within the US.
World Health Organization. MERS. https://www.who.int/health-topics/middle-east-respiratory-syndrome-coronav... (accessed 7/1/2025)
Comment: Coordinating site for MERS-CoV, including clinical, technical and public health implications. Includes link to interim case definition for MERS-CoV infection.

References

Lambrou AS, South E, Midgley CM, et al. Update on the Epidemiology of Middle East Respiratory Syndrome Coronavirus - Worldwide, 2017-2023. MMWR Morb Mortal Wkly Rep. 2025;74(19):313-320. [PMID:40440213]
Comment: Report examines the numbers and impact wtih decline during the COVID pandemic. Diagnostic procedures refined in 2024 (CDC).
Al-Tawfiq JA, Memish ZA. Recurrent MERS-CoV Transmission in Saudi Arabia- Renewed Lessons in Healthcare Preparedness and Surveillance. J Epidemiol Glob Health. 2025;15(1):77. [PMID:40455375]
Comment: Authors from the KSA regarding important detection and management lessons in a country with ongoing cases.
Al-Tawfiq JA. Developments in treatment for middle east respiratory syndrome coronavirus (MERS-CoV). Expert Rev Respir Med. 2024;18(5):295-307. [PMID:38881206]
Comment: Authors looks at all available treatment evidence which is difficult to make strong recommendations as data is limited.
Arabi YM, Asiri AY, Assiri AM, et al. Heterogeneity of treatment effect of interferon-β1b and lopinavir-ritonavir in patients with Middle East respiratory syndrome by cytokine levels. Sci Rep. 2022;12(1):18186. [PMID:36307462]
Comment: A dive into this trial.
Arabi YM, Asiri AY, Assiri AM, et al. Interferon Beta-1b and Lopinavir-Ritonavir for Middle East Respiratory Syndrome. N Engl J Med. 2020;383(17):1645-1656. [PMID:33026741]
Comment: RCT that did find evidence for this combination with better outcomes.
Al-Tawfiq JA, Auwaerter PG. Healthcare-associated infections: the hallmark of Middle East respiratory syndrome coronavirus with review of the literature. J Hosp Infect. 2019;101(1):20-29. [PMID:29864486]
Comment: A review compiling outbreaks and likely reasons why they occurred. Most would be likely prevented with simple isolation and infection control measures.
Alfaraj SH, Al-Tawfiq JA, Memish ZA. Middle East respiratory syndrome coronavirus intermittent positive cases: Implications for infection control. Am J Infect Control. 2019;47(3):290-293. [PMID:30352694]
Comment: Based on data from outbreaks, 2 to 3 nasopharyngeal samples are needed to produce the highest yield of positive results for MERS-CoV. In addition, two negative results 48 hours apart with clinical improvement or stabilization are required to clear patients of MERS-CoV.
Alfaraj SH, Al-Tawfiq JA, Altuwaijri TA, et al. Middle East respiratory syndrome coronavirus transmission among health care workers: Implication for infection control. Am J Infect Control. 2018;46(2):165-168. [PMID:28958446]
Comment: As isolation and infection control are the most effective ways to prevent the spread, simple procedures and protocols are crucial for limiting the spread in healthcare facilities.
Corman VM, Albarrak AM, Omrani AS, et al. Viral Shedding and Antibody Response in 37 Patients With Middle East Respiratory Syndrome Coronavirus Infection. Clin Infect Dis. 2016;62(4):477-483. [PMID:26565003]
Comment: First report of a large patient population summarizing MERS-CoV kinetics and antibody response. The study examines the kinetics of the virus in samples from the upper and lower respiratory tract, stool, urine, and blood.
Zumla A, Hui DS, Perlman S. Middle East respiratory syndrome. Lancet. 2015;386(9997):995-1007. [PMID:26049252]
Comment: Mortality among cases reported so far = ~ 40%, including both community- and hospital-acquired cases. More severe cases are seen primarily in patients with co-morbidities. Now, in the third year, it appears to be endemic and therefore a low-level but persistent public health threat.
Oboho IK, Tomczyk SM, Al-Asmari AM, et al. 2014 MERS-CoV outbreak in Jeddah--a link to health care facilities. N Engl J Med. 2015;372(9):846-54. [PMID:25714162]
Comment: Of 2014 cases in KSA, most had links to hospital care implicating transmission in an arena where opportunities for prevention exist.
Drosten C, Muth D, Corman VM, et al. An observational, laboratory-based study of outbreaks of middle East respiratory syndrome coronavirus in Jeddah and Riyadh, kingdom of Saudi Arabia, 2014. Clin Infect Dis. 2015;60(3):369-77. [PMID:25323704]
Comment: Report from the Kingdom of Saudi Arabia with the most cases, and an uptick in Spring 2014 (and again ongoing in 2015). Viral studies don’t suggest the virus is mutating and appear consistent in outbreaks and nosocomial transmission.
Al-Tawfiq JA, Memish ZA. Infection control measures for the Prevention of MERS Coronavirus Transmission in Healthcare settings. Expert Rev Anti Infect Ther. 2015. [PMID:26687211]
Comment: This is a summary of infection control and prevention of MERS transmission in healthcare settings.
Al-Tawfiq JA, Memish ZA. Managing MERS-CoV in the healthcare setting. Hosp Pract (1995). 2015;43(3):158-63. [PMID:26224424]
Comment: This is a concise review summarizing different aspects of MERS in a healthcare setting including clinical presentation and management.
Al-Tawfiq JA, Memish ZA. Middle East respiratory syndrome coronavirus: transmission and phylogenetic evolution. Trends Microbiol. 2014;22(10):573-9. [PMID:25178651]
Comment: This review shed lights on the different aspects of the transmission and phylogenetic evolution of MERS-CoV.
Al-Tawfiq JA, Hinedi K, Ghandour J, et al. Middle East respiratory syndrome coronavirus: a case-control study of hospitalized patients. Clin Infect Dis. 2014;59(2):160-5. [PMID:24723278]
Comment: A report from the Kingdom of Saudi Arabia examines 17 cases and 82 controls. Cases were more likely to have high BMI, normal WBC count on admission and interstitial infiltrates along with a high mortality rate (76% vs. 15%, p < 0.001).
Briese T, Mishra N, Jain K, et al. Middle East Respiratory Syndrome Coronavirus Quasispecies That Include Homologues of Human Isolates Revealed through Whole-Genome Analysis and Virus Cultured from Dromedary Camels in Saudi Arabia. MBio. 2014;5(3). [PMID:24781747]
Comment: Sequence data from human cases and samples from dromedary camels are identical (in Saudi Arabia), suggesting that camels are indeed a reservoir (known from other studies) and source of some spread to humans.
Al-Tawfiq JA, Memish ZA. Middle East respiratory syndrome coronavirus: epidemiology and disease control measures. Infect Drug Resist. 2014;7:281-7. [PMID:25395865]
Comment: This review summarizes the epidemiology and different strategies for the control of the virus.
Assiri A, Al-Tawfiq JA, Al-Rabeeah AA, et al. Epidemiological, demographic, and clinical characteristics of 47 cases of Middle East respiratory syndrome coronavirus disease from Saudi Arabia: a descriptive study. Lancet Infect Dis. 2013;13(9):752-61. [PMID:23891402]
Comment: Most patients diagnosed to date have had healthcare involvement and hence co-morbidities. Patients were mainly adults in the 47 cases described (46 adults, 1 child) with laboratory-confirmed MERS-CoV disease, and 36 (77%) were male (male: female ratio, 3.3:1). Twenty-eight patients died, a 60% case-fatality rate. The case-fatality rate rose with increasing age. Only two of the 47 cases were previously healthy; most patients (45 [96%]) had underlying co-morbid medical disorders, including diabetes (32 [68%]), hypertension (16 [34%]), chronic cardiac disease (13 [28%]), and chronic renal disease (23 [49%]).
Gastrointestinal symptoms were noted in a significant minority, including diarrhea, vomiting and abdominal pain.
Centers for Disease Control and Prevention (CDC). Update: Recommendations for Middle East respiratory syndrome coronavirus (MERS-CoV). MMWR Morb Mortal Wkly Rep. 2013;62(27):557. [PMID:23842446]
Comment: Initial recommendations for investigating potential cases.
Rating: Important
Assiri A, McGeer A, Perl TM, et al. Hospital outbreak of Middle East respiratory syndrome coronavirus. N Engl J Med. 2013;369(5):407-16. [PMID:23782161]
Comment: Clearly implicating the potential for MERS to cause a serious spread of disease in closer quarters such as hospitals, an outbreak in an eastern province of Saudi Arabia (spring 2013) with 21/23 cases due to person-person spread in healthcare environments. The mortality rate was 65% which may speak to patients with pre-existing illness acquiring.
Perlman S, McCray PB. Person-to-person spread of the MERS coronavirus--an evolving picture. N Engl J Med. 2013;369(5):466-7. [PMID:23902487]
Comment: An outbreak in Al-Hasa, part of eastern Saudi Arabia, implicates direct person-to-person spread.
Zaki AM, van Boheemen S, Bestebroer TM, et al. Isolation of a novel coronavirus from a man with pneumonia in Saudi Arabia. N Engl J Med. 2012;367(19):1814-20. [PMID:23075143]
Comment: The first description of virus, first called HCoV-EMC but now referred to as MERS-CoV, and related but not the cause of SARS, a related coronavirus.
Müller MA, Raj VS, Muth D, et al. Human coronavirus EMC does not require the SARS-coronavirus receptor and maintains broad replicative capability in mammalian cell lines. mBio. 2012;3(6). [PMID:23232719]
Comment: Investigators have helped confirm that this is a sister virus to SARS, and that virus appears to efficiently replicate in cell lines of human, pig, and bat origin.
Al-Tawfiq JA, Zumla A, Memish ZA. Travel implications of emerging coronaviruses: SARS and MERS-CoV. Travel Med Infect Dis. 2014;12(5):422-8. [PMID:25047726]
Comment: This is a nice review of travel implications with comparisons between SARS and MERS-CoV.
Al-Tawfiq JA, Gautret P. Asymptomatic Middle East Respiratory Syndrome Coronavirus (MERS-CoV) infection: Extent and implications for infection control: A systematic review. Travel Med Infect Dis. 2019;27:27-32. [PMID:30550839]
Comment: As with other respiratory viral infections, it seems that asymptomatic patients shedding the virus may contribute to the spread. This makes control more difficult.
Memish ZA, Al-Tawfiq JA, Alhakeem RF, et al. Middle East respiratory syndrome coronavirus (MERS-CoV): A cluster analysis with implications for global management of suspected cases. Travel Med Infect Dis. 2015;13(4):311-4. [PMID:26211569]
Comment: This study summarizes the implications of global MERS cases, highlighting the links between cases in Saudi Arabia and Qatar.

All content is protected by copyright and may not be used for AI model training or other unauthorized purposes.