According to World Health Organization, the interim case definition is that a confirmed case is identified in a person with a positive lab test by "molecular diagnostics including either a positive PCR on at least two specific genomic targets or a single positive target with sequencing on a second". World Health Organization According to the WHO, a probable case is * a person with a fever, respiratory infection, and evidence of pneumonia or acute respiratory distress syndrome, where testing for<unk> -CoV is unavailable or negative on a single inadequate specimen, and the person has a direct link with a confirmed case. * A person with an acute febrile respiratory illness with clinical, radiological, or histopathological evidence of pulmonary parenchymal disease (e.g., pneumonia or acute respiratory distress Syndrome), an inconclusive<unk> -CoV laboratory test (that is, a positive screening test without confirmation), and a resident of or traveler to Middle Eastern countries where<unk> -CoV virus is believed to be circulating in the 14 days before onset of illness. * A person with an acute febrile respiratory illness of any severity, an inconclusive<unk> -CoV laboratory test (that is, a positive screening test without confirmation), and a direct epidemiologic link with a confirmed<unk> -CoV case. Centers for Disease Control In the United States, the Centers for Disease Control and Prevention (CDC) recommend investigating any person with: * Fever and pneumonia or acute respiratory distress syndrome (based on clinical or radiological evidence) and either: * a history of travel from countries in or near the Arabian Peninsula within 14 days before symptom onset, or * close contact with a symptomatic traveler who developed fever and acute respiratory illness (not necessarily pneumonia) within 14 days after traveling from countries in or near the Arabian Peninsula or * a member of a cluster of people with severe acute respiratory illness (e.g. fever and pneumonia requiring hospitalization) of unknown cause in which<unk> -CoV is being evaluated, in consultation with state and local health departments. * Fever and symptoms of respiratory illness (not necessarily pneumonia; e.g., cough, shortness of breath) and being in a healthcare facility (as a patient, worker, or visitor) within 14 days before symptom onset in a country or territory in or near the Arabian Peninsula in which recent healthcare-associated cases of<unk>  have been identified. * Fever or symptoms of respiratory illness (not necessarily pneumonia; e.g., cough, shortness of breath) and close contact with a confirmed<unk>  case while the case was ill. Medical imaging Chest X-ray of a case of<unk>  Chest X-ray findings tend to show bilateral patchy infiltrates consistent with viral pneumonitis and acute respiratory distress syndrome (ARDS). Lower lobes tend to be more involved. CT scans show interstitial infiltrates. Laboratory testing<unk>  cases have been reported to have low white blood cell count, and in particular low lymphocytes. For PCR testing, the World Health Organization (WHO) recommends obtaining samples from the lower respiratory tract via bronchoalveolar lavage (BAL), sputum sample or tracheal aspirate as these have the highest viral loads. There have also been studies utilizing upper respiratory sampling via nasopharyngeal swab. Several highly sensitive, confirmatory real-time RT-PCR assays exist for rapid identification of<unk> -CoV from patient-derived samples. These assays attempt to amplify upE (targets elements upstream of the E gene), open reading frame 1B (targets the ORF1b gene) and open reading frame 1A (targets the ORF1a gene). The WHO recommends the upE target for screening assays as it is highly sensitive. In addition, hemi-nested sequencing amplicons targeting RdRp (present in all coronaviruses) and nucleocapsid (N) gene (specific to<unk> -CoV) fragments can be generated for confirmation via sequencing. Reports of potential polymorphisms in the N gene between isolates highlight the necessity for sequence-based characterization. The WHO recommended testing algorithm is to start with an upE RT-PCR and if positive confirm with ORF 1A assay or RdRp or N gene sequence assay for confirmation. If both an upE and secondary assay are positive it is considered a confirmed case. Protocols for biologically safe immunofluorescence assays (IFA) have also been developed; however, antibodies against betacoronaviruses are known to cross-react within the genus. This effectively limits their use to confirmatory applications. A more specific protein-microarray based assay has also been developed that did not show any cross-reactivity against population samples and serum known to be positive for other betacoronaviruses. Due to the limited validation done so far with serological assays, WHO guidance is that "cases where the testing laboratory has reported positive serological test results in the absence of PCR testing or sequencing, are considered probable cases of<unk> -CoV infection, if they meet the other conditions of that case definition."
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