History and exam

Key diagnostic factors

commonVIEW ALL

residence in, or travel to, the Middle East (or country where there is an active outbreak) in previous 14 days

All confirmed cases have either resided in, or traveled to, the Middle East in the 14 days prior to the onset of symptoms.[98][99][100][101] This includes the Arabian Peninsula (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, United Arab Emirates, Yemen) and its surrounding countries (Iraq; Iran; Israel, the West Bank, and Gaza; Jordan; Lebanon; Syria).

age >14 years

Ninety-eight percent of cases have been reported in adults (defined as age >14 years).[102]

Infection in children is rare, although the reason for this is unknown.[103][104]

fever

Reported in 40% to 98% of cases.[105][102][106]

Fever may be absent in older patients, immunocompromised patients, pregnant women, and patients with end-stage renal disease, diabetes mellitus, or hemochromatosis;[107] therefore, absence of fever should not preclude workup for MERS.[108]

cough

Reported in 54% to 86% of cases. It is usually dry; however, has been reported to be productive in 23% to 36% of patients.[102][106][109]

dyspnea

Reported in 60% to 72% of cases.[102][106][109]

Other diagnostic factors

commonVIEW ALL

hemoptysis

Reported in 7% to 17% of cases.[102][106][109]

diarrhea

Reported in 7% to 26% of cases.[107][102][106]

abdominal pain

Reported in 17% to 24% of cases.[102][109]

nausea/vomiting

Reported in 7% to 21% of cases.[107][102][106]

chills/rigors

Usually associated with fever.

myalgia

Nonspecific symptom reported in some cases.[110][107][111][105][102][106]

arthralgia

Nonspecific symptom reported in some cases.[110][107][111][105][102][106]

malaise

Nonspecific symptom reported in some cases.[110][107][111][105][102][106]

headache

Nonspecific symptom reported in some cases.[110][107][111][105][102][106]

sore throat

Nonspecific symptom reported in some cases.[110][107][111][105][102][106]

rhinorrhea

Nonspecific symptom reported in some cases.[110][107][111][105][102][106]

tachypnea

Present in some cases, including patients with acute respiratory distress.

tachycardia

Present in some cases, including patients with acute respiratory distress.

cyanosis

Present in some cases, including patients with acute respiratory distress.

chest pain

May indicate pneumonia.

crackles/rales on auscultation

May indicate pneumonia.

Bronchial breath sounds may also be heard.

Risk factors

strongVIEW ALL

residence in, or travel to, the Middle East (or country where there is an active outbreak) in previous 14 days

All confirmed cases have either resided in, or traveled to, the Middle East in the 14 days prior to the onset of symptoms.[17][19][79][80] This includes the Arabian Peninsula (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, United Arab Emirates, Yemen) and its surrounding countries (Iraq; Iran; Israel, the West Bank, and Gaza; Jordan; Lebanon; Syria).

close contact with infected individuals

Majority of cases are a result of human-to-human transmission (rather than camel-to-human transmission) with peaks of confirmed cases occurring during nosocomial outbreaks.[6][7][28]

Transmission has been well documented in family clusters.[18][29][30] However, it has been reported more commonly in nosocomial outbreaks (e.g., hemodialysis units, intensive care units, medical wards).[6][7][30][31][32][33]

Transmission is via respiratory droplets (e.g., coughing, sneezing) from an infected patient, or close contact with an infected patient. However, airborne or fomite transmission cannot be ruled out.[65] The incubation period is 2 to 14 days and transmission is thought to occur during either the symptomatic or incubation stages.[8][66]

All patients diagnosed outside of the Middle East have been in contact with someone who has traveled from the Middle East in the preceding 14 days.[17][19][79][80]

exposure to infected dromedary camels

Dromedary camels are thought to be the primary animal host.[39]

Exact mode of transmission is unknown, but it is thought to occur from direct or indirect contact with dromedary camels (e.g., camel milking, contact with camel nasal secretions, urine, or feces) or camel products (e.g., unpasteurized camel milk, raw or undercooked camel meat).

Strongest evidence for camel-to-human transmission comes from a study in Saudi Arabia where the virus was isolated from a patient and one of his camels and the genome was found to be almost identical.[61][62]

A case-control study identified contact with camels to be a risk factor.[64]

age ≥50 years

Although infection has been reported in different age groups within the adult population, the median age of patients ranges from 50 to 67 years of age.[4][9][26]

Age ≥50 years is associated with more severe presentation, worse outcomes, and a higher risk of mortality.[5][27] In one cohort study, mortality increased with increasing age to reach 75% in patients >60 years of age.[8]

diabetes mellitus

Reported in 65% to 87% of confirmed cases and has been associated with severe infection.[5][8][9][26]

Most common comorbid condition in one cohort of 12 critically ill patients admitted to the intensive care unit.[81]

Identified as a risk factor in a case-control study.[64]

chronic renal impairment

Reported in 33% of confirmed cases (compared with 7% of patients who were initially suspected of being infected but who later tested negative).[9]

Patients with end-stage renal disease were reported to develop severe infection and had worse clinical outcomes.[81] In one case series, a mortality rate of 100% was reported in patients with chronic renal impairment, including 8 patients who were undergoing hemodialysis.[5]

May be related to the immune dysregulation that occurs in patients with end-stage renal disease on hemodialysis.[82]

heart disease

Identified as a risk factor in a case-control study.[64]

obesity

Patients with confirmed infection had a median BMI of 32 compared with 27.8 in controls in one case-control study.[9]

Reported to be associated with severe infection and worse clinical outcomes in several case series.[8][81]

tobacco smoking

Identified as a risk factor in a case-control study.[64]

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