History and exam

Key diagnostic factors

common

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 travelled to, the Middle East in the 14 days prior to the onset of symptoms.​[17][19][64][65]​​ 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).[8]​​

Infection in children is rare, although the reason for this is unknown.[13]​​[14]​​

fever

Reported in 40% to 98% of cases.[8][7][9][10]

Fever may be absent in older patients, immunocompromised patients, pregnant women, and patients with end-stage renal disease, diabetes mellitus, or haemochromatosis; therefore, absence of fever should not preclude work-up for MERS.[5][72]​​

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.[8][9][10]

dyspnoea

Reported in 60% to 72% of cases.[8][9][10]

Other diagnostic factors

common

haemoptysis

Reported in 7% to 17% of cases.[8]​​[9][10]

diarrhoea

Reported in 7% to 26% of cases.[5][8][9][10]

abdominal pain

Reported in 17% to 24% of cases.​[8][10]

nausea/vomiting

Reported in 7% to 21% of cases.[5][8][9][10]

chills/rigors

Usually associated with fever.

myalgia

Non-specific symptom reported in some cases.[4][5][6][7][8][9][10]

arthralgia

Non-specific symptom reported in some cases.[4][5][6][7][8][9][10]

malaise

Non-specific symptom reported in some cases.[4][5][6][7][8][9][10]

headache

Non-specific symptom reported in some cases.[4][5][6][7][8][9][10]

sore throat

Non-specific symptom reported in some cases.[4][5][6][7][8][9][10]

rhinorrhoea

Non-specific symptom reported in some cases.[4][5][6][7][8][9][10]

tachypnoea

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

strong

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 travelled to, the Middle East in the 14 days prior to the onset of symptoms.[17]​​[19]​​[64][65] 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., haemodialysis units, intensive care units, medical wards).[6]​​[7]​​[29]​​[30]​​[31]​​[32]​​

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.[50] The incubation period is 2 to 14 days and transmission is thought to occur during either the symptomatic or incubation stages.[8]​​[51]

All patients diagnosed outside of the Middle East have been in contact with someone who has travelled from the Middle East in the preceding 14 days.[17]​​[19]​​[64][65]

exposure to infected dromedary camels

Dromedary camels are thought to be the primary animal host.[36]​​

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 faeces) or camel products (e.g., unpasteurised 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.[46][47]

A case-control study identified contact with camels to be a risk factor.[49]

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