Criteria
Case definitions
Case definitions have been published by the World Health Organization (WHO) and Ministry of Health (Saudi Arabia).[73][74]
The Centers for Disease Control and Prevention (CDC) simply defines a confirmed case as a person who has laboratory evidence of MERS-CoV infection using molecular testing.[82]
Because MERS is considered an emerging disease, definitions are constantly evolving and not all clinical presentations will fit the case definitions. Physicians should be vigilant for identifying suspected cases, regardless of whether they fit the case definitions or not. For example, the absence of fever has been reported in cases of confirmed infection, despite some definitions including fever as a prerequisite for diagnosis.
WHO: case definition for reporting to WHO[74]
Probable case:
A febrile acute respiratory illness with clinical, radiological, or histopathological evidence of pulmonary parenchymal disease (e.g., pneumonia or acute respiratory distress syndrome) + a direct epidemiological link with a confirmed case + testing is unavailable, negative on a single inadequate specimen, or inconclusive
A febrile acute respiratory illness with clinical, radiological, or histopathological evidence of pulmonary parenchymal disease (e.g., pneumonia or acute respiratory distress syndrome) + the person resides in, or travelled to, the Middle East or in countries where the virus is known to be circulating in dromedary camels or where infections have recently occurred + testing is inconclusive
An acute febrile respiratory illness of any severity + a direct epidemiological link with a confirmed case + testing is inconclusive.
Confirmed case:
Person with laboratory confirmation (i.e., detection of viral nucleic acid or serology) of infection irrespective of clinical signs and symptoms. Presence of nucleic acid can be confirmed by either a positive RT-PCR result on at least two specific genomic targets or a single positive target with sequencing of a second target. Cases confirmed by serology require demonstration of seroconversion in two samples, ideally taken 14 days apart, by ELISA or immunofluorescence antibody assay and a neutralisation assay.
World Health Organization (WHO): case definition for reporting to WHO Opens in new window
Ministry of Health (Saudi Arabia): case definition[73]
Suspected case:
I. Severe pneumonia (severity score ≥3 points on CURB 65) or acute respiratory distress syndrome (based on clinical or radiological evidence) [ CURB-65 pneumonia severity score Opens in new window ]
II. Unexplained deterioration of a chronic condition in patients with congestive heart failure or chronic kidney disease who are on haemodialysis
III. Acute febrile illness with or without respiratory symptoms + an epidemiologic link
IV. Gastrointestinal symptoms and leukopenia or thrombocytopenia + an epidemiologic link.
Confirmed case:
A suspected case with laboratory confirmation of infection.
An epidemiologic link is defined as one of the following within 14 days before symptom onset:[73]
Exposure (contact within 1.5 metres) to a confirmed case of MERS-CoV infection
Visit to a healthcare facility where an infected patient has recently (within 2 weeks) been identified or treated
Contact with dromedary camels or consumption of camel products.
Ministry of Health (Saudi Arabia): case definition Opens in new window
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