Based on cases reported from April 2012 to March 2024, the case fatality rate is approximately 36%. The case fatality rate is highest in people ages 70 to 79 years.[25]World Health Organization. Middle East respiratory syndrome. May 2024 [internet publication].
https://www.emro.who.int/health-topics/mers-cov/mers-outbreaks.html
This fatality rate is lower than previously reported rates in the literature as cohort studies generally include only patients who are sick enough to require hospitalization.[5]Shalhoub S, Farahat F, Al-Jiffri A, et al. IFN-alpha-2a or IFN-beta-1a in combination with ribavirin to treat Middle East respiratory syndrome coronavirus pneumonia: a retrospective study. J Antimicrob Chemother. 2015;70:2129-32.
http://www.ncbi.nlm.nih.gov/pubmed/25900158?tool=bestpractice.com
[8]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 Sep;13(9):752-61.
https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(13)70204-4/fulltext#seccestitle10
http://www.ncbi.nlm.nih.gov/pubmed/23891402?tool=bestpractice.com
[9]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 Jul 15;59(2):160-5.
https://academic.oup.com/cid/article/59/2/160/2895452
http://www.ncbi.nlm.nih.gov/pubmed/24723278?tool=bestpractice.com
[27]Omrani AS, Saad MM, Baig K, et al. Ribavirin and interferon alfa-2a for severe Middle East respiratory syndrome coronavirus infection: a retrospective cohort study. Lancet Infect Dis. 2014;14:1090-5.
http://www.ncbi.nlm.nih.gov/pubmed/25278221?tool=bestpractice.com
Age ≥50 years has been associated with more severe presentation, worse outcomes, and a higher risk of mortality.[5]Shalhoub S, Farahat F, Al-Jiffri A, et al. IFN-alpha-2a or IFN-beta-1a in combination with ribavirin to treat Middle East respiratory syndrome coronavirus pneumonia: a retrospective study. J Antimicrob Chemother. 2015;70:2129-32.
http://www.ncbi.nlm.nih.gov/pubmed/25900158?tool=bestpractice.com
[10]Saad M, Omrani AS, Baig K, et al. Clinical aspects and outcomes of 70 patients with Middle East respiratory syndrome coronavirus infection: a single-center experience in Saudi Arabia. Int J Infect Dis. 2014;29:301-6.
http://www.ijidonline.com/article/S1201-9712(14)01622-1/fulltext
http://www.ncbi.nlm.nih.gov/pubmed/25303830?tool=bestpractice.com
In one cohort study, mortality increased with increasing age to reach 75% in patients >60 years of age.[8]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 Sep;13(9):752-61.
https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(13)70204-4/fulltext#seccestitle10
http://www.ncbi.nlm.nih.gov/pubmed/23891402?tool=bestpractice.com
Presence of comorbidities (e.g., diabetes mellitus, chronic renal impairment, heart disease, obesity) increases the risk of acute respiratory failure and worse outcomes.[5]Shalhoub S, Farahat F, Al-Jiffri A, et al. IFN-alpha-2a or IFN-beta-1a in combination with ribavirin to treat Middle East respiratory syndrome coronavirus pneumonia: a retrospective study. J Antimicrob Chemother. 2015;70:2129-32.
http://www.ncbi.nlm.nih.gov/pubmed/25900158?tool=bestpractice.com
[8]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 Sep;13(9):752-61.
https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(13)70204-4/fulltext#seccestitle10
http://www.ncbi.nlm.nih.gov/pubmed/23891402?tool=bestpractice.com
[9]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 Jul 15;59(2):160-5.
https://academic.oup.com/cid/article/59/2/160/2895452
http://www.ncbi.nlm.nih.gov/pubmed/24723278?tool=bestpractice.com
[27]Omrani AS, Saad MM, Baig K, et al. Ribavirin and interferon alfa-2a for severe Middle East respiratory syndrome coronavirus infection: a retrospective cohort study. Lancet Infect Dis. 2014;14:1090-5.
http://www.ncbi.nlm.nih.gov/pubmed/25278221?tool=bestpractice.com
[71]Arabi YM, Arifi AA, Balkhy HH, et al. Clinical course and outcomes of critically ill patients with Middle East respiratory syndrome coronavirus infection. Ann Intern Med. 2014;160:389-397.
http://annals.org/aim/article/1817260/clinical-course-outcomes-critically-ill-patients-middle-east-respiratory-syndrome
http://www.ncbi.nlm.nih.gov/pubmed/24474051?tool=bestpractice.com
Natural course of infection
As the clinical presentation is highly variable and ranges from no symptoms to rapidly progressive pneumonia, the natural course is also variable.
The median time from symptom onset to death ranges from 16.5 to 20.5 days in cohort studies.[8]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 Sep;13(9):752-61.
https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(13)70204-4/fulltext#seccestitle10
http://www.ncbi.nlm.nih.gov/pubmed/23891402?tool=bestpractice.com
[10]Saad M, Omrani AS, Baig K, et al. Clinical aspects and outcomes of 70 patients with Middle East respiratory syndrome coronavirus infection: a single-center experience in Saudi Arabia. Int J Infect Dis. 2014;29:301-6.
http://www.ijidonline.com/article/S1201-9712(14)01622-1/fulltext
http://www.ncbi.nlm.nih.gov/pubmed/25303830?tool=bestpractice.com
Median time to viral clearance, documented by negative real-time reverse transcription polymerase chain reaction (RT-PCR) on respiratory specimens, is 11 days (range 6 to 35 days).[5]Shalhoub S, Farahat F, Al-Jiffri A, et al. IFN-alpha-2a or IFN-beta-1a in combination with ribavirin to treat Middle East respiratory syndrome coronavirus pneumonia: a retrospective study. J Antimicrob Chemother. 2015;70:2129-32.
http://www.ncbi.nlm.nih.gov/pubmed/25900158?tool=bestpractice.com
[138]Poissy J, Goffard A, Parmentier-Decrucq E, et al. Kinetics and pattern of viral excretion in biological specimens of two MERS-CoV cases. J Clin Virol. 2014;61:275-278.
http://www.ncbi.nlm.nih.gov/pubmed/25073585?tool=bestpractice.com
In patients who survived, median time from symptom onset to discharge from hospital was 27 days (range 20 to 31.5 days).[10]Saad M, Omrani AS, Baig K, et al. Clinical aspects and outcomes of 70 patients with Middle East respiratory syndrome coronavirus infection: a single-center experience in Saudi Arabia. Int J Infect Dis. 2014;29:301-6.
http://www.ijidonline.com/article/S1201-9712(14)01622-1/fulltext
http://www.ncbi.nlm.nih.gov/pubmed/25303830?tool=bestpractice.com
Recurrence of infection in patients who have recovered has not been reported. There are currently no data on whether previous infection offers protection against future infection.