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Table 2 Factors related to infection, transmission, severity, and mortality of MERS

From: MERS transmission and risk factors: a systematic review

Author (year) Study period No. of participants
Country Predictors Significant factors
Risk factors of infection
 Alraddadi (2016) [42] 2014 146 (30 cases, 116 controls) Saudi Arabia Travel history, animal-related exposure, food exposure, underlying health conditions and behaviors Direct dromedary exposure in 2 weeks, concomitant with diabetes or heart disease, currently smoking tobacco
 Hastings (2016) [43] 2014 78 Saudi Arabia Nationality, sex, age group, hospital setting, outbreak week Older age, outbreak week, nationality
Risk factors of transmission (spreader)
 Kang (2017) [44] 2015 186 South Korea Age, sex, comorbidity, symptoms, laboratory test, clinical outcome, phase in transmission, incubation period, symptom onset to isolation, non-isolated in-hospital days, symptom onset to diagnosis Fever, chest X-ray abnormality in > 3 lung zones, more non-isolated in-hospital days
 Kim (2017) [34] 2015 186 South Korea Underlying respiratory disease, cycle threshold value, symptom onset to diagnosis, no. of contacts, hospitalization or emergency room before isolation Lower cycle threshold value, hospitalization or emergency room visit before isolation
 Majumder (2017) [45] 2015 186 South Korea Sex, age, comorbidity, case class (HCW, visitor, patient), case outcome (recovered/deceased) Deceased case outcome
Risk factors of severity
 Zhao (2017) [46] 2014–2015 21 Saudi Arabia CD4 T cell, CD8 T cell, PRNT50 Higher PRNT50, higher CD4 T cell response
 Ko (2016) [48] 2015 45 South Korea Demographics (age, sex, BMI, underlying disease), symptoms (fever, myalgia, cough, sputum, diarrhea), laboratory test (white blood cell, hemoglobin, thrombocytopenia, lymphopenia, albumin, bilirubin, aspartate transaminase, alanine transaminase, blood urea nitrogen, creatinine, C-reactive protein, lactate dehydrogenase, threshold cycle value of PCR) • Pneumonia development: older age, fever, thrombocytopenia, lymphopenia, C-reactive protein ≥2 mg/dL, lower threshold cycle value of PCR < 28
• Respiratory failure: male, hypertension, low albumin concentration, thrombocytopenia, lymphopenia, C-reactive protein
 Feikin (2015) [47] 2014 102 Saudi Arabia Age, sex, underlying illness, week of specimen collection, MERS-CoV virus load • Severity: older age, underlying illness, high MERS-CoV virus load
• Mortality: older age, underlying illness, high MERS-CoV virus load
 Saad (2014) [49] 2012–2014 70 Saudi Arabia Age, gender, occupation, acquisition of infection, comorbidity, radiological findings, concomitant infections, laboratory abnormalities • ICU care: concomitant infection, decreased albumin
• Mortality: older age
Risk factors of mortality
 Adegboye (2017) [50] 2012–2015 959/317 (33%) Saudi Arabia Sex, age, comorbidity, animal contact, camel contact, HCW, secondary contact, clinical experience Older age, comorbidity, non-HCW, fatal clinical experience
 Ahmed (2017) [51] 2014–2016 660/197 (29.8%) Saudi Arabia Age, sex, nationality, symptomatic, HCW, severity, source of infection, regions • 3-day mortality: older age, non-HCW, hospital-acquired infection
• 30-day mortality: older age, non-HCW, pre-existing illness, severity, hospital-acquired infection
 Sha (2017) [29] 2012–2016 216/56 (25.9%) in Middle East area, 174/24 (13.8%) in South Korea Middle East Area/South Korea Age, sex, exposure to camel or other animals, comorbidity, disease progress (days) Older age (Middle East, South Korea), high comorbidity (Middle East, South Korea), longer days from onset to confirmation of infection (Middle East), longer hospitalized days (Middle East)
 Sherbini (2017) [32] 2014 29/10 (34.5%) Saudi Arabia Sex, symptoms, history of chronic disease, duration of disease before hospitalization, vital signs, temperature, blood pressure Older age, gastrointestinal symptoms, longer duration of symptoms prior to hospitalization, diabetes mellitus, chronic kidney disease, smokers, lower blood pressure
 Nam (2017) [56] 2015 25/11 (44%) South Korea - Epidemiologic (age, sex, hospital, inpatient, staying in the same room as the index case, smoking, preexisting pneumonia, chronic lung disease, incubation period)
- Clinical symptom
- Laboratory examinations
Male, pre-existing pneumonia, smoking history, incubation period of less than 5 days, leukocytosis, abnormal renal function at diagnosis, respiratory symptoms.
 Yang (2017) [52] 2012–2016 1743/559 (32.1%) Multiple area Age, sex, comorbidity, epidemic period, contact pattern, country Older age, comorbidity, epidemic later period
 Almekhlafi (2016) [57] 2012–2014 31/23 (74.2%) Saudi Arabia Age, comorbidity, initial manifestations, procedures (non-invasive ventilation, invasive ventilation, continuous renal replacement therapy), need for vasopressor Need for vasopressors
 Alsahafi (2016) [53] 2012–2015 924/ 425 (46%) Saudi Arabia Age, sex, comorbidities, location of acquisition (household, inpatient, HCW) Older age, cardiac disease, cancer, household patients, HCW
 Virlogeux (2016) [25] 2015 170/36 (21%) South Korea Age, sex, incubation period Older age, shorter incubation period
 Cha (2015) 2015 30/5 (16.7%) South Korea Age, sex, chronic kidney disease, diabetes, hypertension, comorbidity, estimated glomerular filtration rate, mechanical ventilator None
 Majumder (2015) [54] 2015 159/35 (22%) South Korea Five potential covariates were analyzed: sex, age, concurrent health condition status, health care worker status, time from onset to diagnosis Older age, pre-existing concurrent health conditions
 KCDC (2015) [4] 2015 186/36 (19.4%) South Korea Sex, age, case classification, respiratory disease, diabetes, cardiac disease, chronic kidney disease, malignancy Older age, underlying respiratory disease
 Das (2015) [58] 2014 55/19 (35%) Saudi Arabia Age, chest radiographic score, absolute lymphocyte count, no. of comorbidities, congestive heart failure, hypertension, diabetes Chest radiographic score
 Al Ghamdi (2016) [59] 2014 51/19 (37%) Saudi Arabia Beta interferon, alpha interferon, hydrocortisone, Ribavirin, APACHE score APACHE score
 Choi (2016) [55] 2016 186/33 (17.7%) South Korea Age, sex, HCW, coexisting medical condition, symptoms at admission, vital signs at admission, laboratory abnormalities at admission, treatment Age ≥ 55 years, occurrence of dyspnea during the disease course, presence of concomitant medical conditions including diabetes or chronic lung disease, systolic blood pressure < 90 mmHg at admission, leukocytosis at admission, use of mechanical ventilation
  1. APACHE acute physiologic and chronic health evaluation, ICD intensive care unit, HCW healthcare worker, PCR polymerase chain reaction, PRNT plaque reduction neutralization test