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Table 1 Epidemiologic studies of MERS, 2012–2017

From: MERS transmission and risk factors: a systematic review

Author (year) Country Study period No. of patients
(M/F)
Age of patients
Fatality rate Contact/ comorbidity Index related to infectivity Index related to severity
 Ahmed (2017) [31] Saudi Arabia 2015–2017 537 (370/167)
55 ± 17.9
218/537 (40.6%) • Comorbidity: 73.9%
• Contacts
- Hospital-acquired: 38.7%
- Household: 9.9%
- Camel: 25.3%
- Unknown: 26.1%
  • Onset to confirmation: 4 days (IQR: 2–7 days)
 Alenazi (2017) [12] Saudi Arabia 2015 130 (66/64)
63.5 (community-acquired), 64.7 (healthcare-acquired), 40.1 (HCW)
51/130 (39.2%) • Contacts
- Community-acquired: 20%
- Healthcare-acquired: 46.9%
- HCWs: 33.1%
• R
- Hospital-acquired: 0.98 for 2nd, 0.64 for 3rd, 0.23 for 4th generation
 
 El- Bushra (2017) [21] Saudi Arabia 2015 87
n.r.
n.r. • Contacts
- 20 primary, 39 first, 18 s, 7 third, 3 fourth generation
• Secondary attack rate/10,000: 42 (95% CI: 33–54)  
 Kim (2017) South Korea 2015 186 (111/75)
55
38/186
(19.9%)
• Contacts
- Hospital (99.4%)
- Household (0.6%)
- Community (0%)
• Comorbidity
- 29/38 fatalities had underlying disease
  
 Park (2017) [23] South Korea 2015 25 (13/12)
71a (IQR: 38–86)
25/11 (44.0%)   • Attack rate: 3.7%
• Incubation period: 6.1 days
 
 Sha (2017) [29] Middle East area/
South Korea
2012–2016 683 (423/260)
50–60 (fatal), 38–46 (non-fatal)
182 (26.6%)
(Middle East: 25.9%,
South Korea: 13.8%)
• Comorbidity
- 67.9% in fatal, 22.2% in nonfatal cases
• Incubation period
- 4.5–5 days in Middle East area
- 6 days in South Korea
• Onset to confirmation
- 8 days in fatal, 4 days in nonfatal in Middle East area
- 4 days in fatal, 5 days nonfatal in South Korea
• Onset to death
- 11.5 days in Middle East area
- 11 days in South Korea
• Onset to discharge
- 14 days in Middle East area
- 17 days in South Korea
 Sherbini (2017) [32] Saudi Arabia 2014 29 (20/9)
45 ± 12
10 (34%) • Comorbidities
- Diabetes (31%)
- Chronic kidney disease (27%)
  • Symptoms to hospitalization: 2.9–5 days
 Assiri (2016) [36] Saudi Arabia 2014–2015 38 (28/10)
51 (range 17–84)
21/38 (55.3%) • Contacts
- 13 HCWs
- 15 were associated with 1 dialysis unit
  • Onset to death/discharge: 17 days (range 1.0–84.0)
 Cho (2016) [5] South Korea 2015 82 (53/29)
57 (patients and visitors),
38 (HCW)
n.r. • Contacts
- Patients: 40.2%
- Visitors: 50%
- HCWs: 9.8%
• Comorbidity
- 24 (29%) had underlying disease
• Incubation period: 7 days (range: 2–17, IQR: 5–10)
• Overall attack rate
- Patients in the emergency room: 4% (30/ 675)
- Visitors: 6% (38/683)
 
 Halim (2016) [33] Saudi Arabia 2016 32 (20/12)
43.99 ± 13.03
14/32 (43.8%)    • From symptom to hospitalization
- 5.3 ± 3.3 days
• Total length of stay
- 15 ± 3.6 days
 Liu (2016) Taiwan 2012–2015 1368 (883/476)a
49 (range: 2–90)
35.6% (487/1368)
• CFR
7.03% for HCW
- 36.96% for non-HCW
• Contacts
- Patients: 46.2%
- Family members or visitors: 34.9%
- HCW: 18.9%
  • Onset to death
- 13 (4–17) days for HCP
- 12 (1–52) days for non-HCW
• Onset to confirmation
- 6 (1–14) days for HCP
- 10 (1–21) days for non-HCW
 Mohd (2016) [40] Saudi Arabia 2014–2015 80 (48/32)
40a
• 10% (8/80) • Comorbidity
- Not different from non-MERS groups
  
 Park (2016) [24] South Korea 2015 23 (13/10)
66a (range: 31–87) in hospital A;
74.5a (range: 60–82) in hospital B
11/23 (47.8%) • Generation
- 23 in 2nd; 3 in 3rd
• Incubation period
- 7.8 days (95% CI: 6.0–10.0)
• Serial interval
- 14.6 days (95% CI, 12.9–16.5)
• Secondary attack rate
- 15.8% in hospital A
- 14.3% in hospital B
• Time to deathc
- 12.5 days (IQR: 5.5–19) in hospital A
- 11 days (IQR: 9–16) in hospital B
 Virlogeux (2016) [25] South Korea 2015 170 (98/72)
54.6 ± 16.2
36/170 (21%)   Incubation period: 6.9 days (95% CI: 6.3–7.5)  
 Chowell (2015) [8] Saudi Arabia, South Korea 2013–2015 973 MERS and 7634 SARS cases
n.r.
n.r. • Contacts
- 43.5–100% were linked to healthcare setting in MERS
R0 (95% CI)
- MERS: 0.91 (0.36–1.44)
- SARS: 0.95 (0.67–1.23)
Infection rate of disease among HCWs:
- MERS: 13.4–13.5%
- SARS: 18.8–57.1%
 
 Cowling (2015) [26] South Korea 2015 166 (101/65)
55.4 (range: 16–87)
24/166 (14.5%) • Contacts
- 119 cases had contact with a confirmed case
- 30/166 (18%) were healthcare personnel
• Incubation period: 6.7 days
• Serial interval: 12.6 days.
 
 KCDC (2015) [4] South Korea 2015 186 (111/75)
55a (IQR: 42–66)
36/186 (19.4%) • Contacts
- 44.1% patients exposed in hospitals
- 32.8% caregivers
- 13.4% HCWs
• Comorbidities
- 45.2%
• Incubation period
- 6.83 days (95% CI: 6.31,7.36)
 
 Ki (2015) [3] South Korea 2015 186 (111/75)
50s in men and 60s in women
36/186 (19.4%) • Generation
- 28 in 1st (15.1%); 125 in 2nd (67.2%); 32 in 3rd (17.2%); 2 were not certain
• Contacts
- Same hospital: 82 (44%)
- Family/healthcare aides/visitors: 71 (38%)
- HCWs: 31 (17%)
• Comorbidities
- 77 (41%) had underlying diseases
• Incubation period: 6.5 days (2–16 days). • From symptom onset to confirmation: 5 days (0–17 days)
• From symptom onset to discharge from the hospital: 20 days (8–41 days).
• From symptom onset to death: 13 days (1–41 days)
 Ministry of Health, South Korea (2016) [27] South Korea 2015 186 (111/75)
50s (21.6%), 60s (19.9%)
38/186 (20.4%) • Generation
- 28 in 2nd, 120 in 3rd, 26 in 4th, 11 in unclear/
unknown
• Contacts
- 82 patients in hospital - 63 family members/
visitors
- 39 HCWs
- 2 others
• Incubation period
- 6.83 days (95% CI: 6.31–7.36)
 
 Noorwali (2015) [37] Saudi Arabia 2014 261 (171/90)
n.r.
110/261 (42%) • Contacts
- 84 HCWs
- 177 non-HCWs
  
 Park (2015) [28] South Korea 2015 37 (21/16)
51.7 (range: 24–79)
6/37 (16.2%) • Generation
- 1 in 1st, 25 in 2nd, 11 in 3rd
• Contacts
- 20 patients
- 12 relatives of patients
- 3 HCWs
- 1 unrelated visitors
• Comorbidities
- 5/6 in fatal, 3/31 in nonfatal
Incubation period
- 6 days (95% CI: 4–7 days)
• Symptom onset to confirmation
- 6.5 days (95% CI: 4–9) for all cases
- 9 days for second cases
- 4 days for third cases
 Drosten (2014) [22] Saudi Arabia 2013 26 (17/9)
55a (range: 2–83)
18/26 (69.2%) • Contacts
- 280 household contacts
• Secondary transmission: 4%  
 Assiri (2013) [7] Saudi Arabia 2012–2013 47 (36/11)
n.r.
28/47 (60%) • Comorbidities
- 45 had underlying comorbid medical disorders (96%)
• Incubation period: 5.2 days  
 Breban (2013) [9] Multiple areas 2012–2013 64 (44/17) b
56a (IQR 41–68.5)
38/64 (59.4%) n.r. • R0: 0.69 (95% CI 0.50–0.92)  
 Oboho (2012) [38] Saudi Arabia 2014 255 (174/81)
45a (IQR:30–59)
93 (36.5%) • Contacts
- 40 of 191 symptomatic were HCWs (20.9%)
  n.r.
 Penttinen (2013) [41] Multiple areas 2012–2013 133 (51/77) b
n.r.
45% • Contacts
- 14 primary cases, 129 cases on transmission
  • Proportion to ICU:
60 cases (45%)
Estimating the index of infectivity and severity using secondary data
Author (year) Country Study period Indexes related to infectivity Index related to severity
 Chang (2017) [18] South Korea 2015 • R0
- 8.097
 
 Choi (2017) [15] South Korea, Saudi Arabia 2015 • R0
- 3.9 in South Korea
- 1.9–3.9 in Saudi Arabia (1.9 in Riyadh, 3.9 in Jeddah)
 
 Eifan (2017) [13] Saudi Arabia 2013–2015 • R
- 0.85–0.97
 
 Zhang (2017) [17] South Korea 2015 • R
- 2.5–7.2
 
 Kim (2016) [16] South Korea 2015 • R0
- 5.4 (95% CI: 4.61–6.19) in period 1
- 0.14 (95% CI: 0.04–0.26) in period 2
• Infectivity of hospitalized patients
- 22 (95% CI: 18.73–25.27) in period 1
- 1 (95% CI: 0.16–1.84) in period 2
 
 Lessler (2016) [39] Saudi Arabia 2012–2014   • CFR: 22% (95% CI: 18, 25)
 Kucharski (2015) [10] Multiple areas 2012–2013 • R0: 0.47 (95% CI: 0.29–0.80)  
 Mizumoto (2015) [35] South Korea 2015   • CFR: 20.0% (95% CI): 14.6, 26.2).
 Xia (2015) [19] South Korea 2015 • R0
- 4.422 in early stage
- 0.385 with control
from hospitalization to death: 15.16 (0–42) (mean, range)
 Cauche-mez (2014) [6] Multiple areas 2012–2013 • Incubation period
- 5.5 (95% CI: 3.6–10·2)
• R0: 0.8–1.3
• CFR
- 74% (95% CI: 49–91) for first cases
- 21% (95% CI: 7–42) for second cases
 Chowell (2014) [11] Saudi Arabia 2013 • R overall
- 0.45 (95% CI: 0.29, 0.61) under the surveillance-bias scenario
- 0.88 (95% CI: 0.58, 1.20) under the differential-transmissibility scenario
 
 Poletto (2014) [14] Middle East area 2012–2013 • R: 0.50 (95% CI: 0.30–0.77)  
  1. CI confidence interval, ICU intensive care unit, IQR interquartile range, HCW healthcare worker, SARS severe acute respiratory syndrome
  2. aMedian age, the others are mean age
  3. bInformation of several participants was missing
  4. cDefinition is not clear in this study