History and exam

Key diagnostic factors

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).

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]

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]

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]

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

Other diagnostic factors

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

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

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

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

Usually associated with fever.

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

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

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

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

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

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

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

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

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

May indicate pneumonia.

May indicate pneumonia.

Bronchial breath sounds may also be heard.

Risk factors

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).

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]

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]

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]

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]

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]

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

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]

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

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