MERS Clinical Features
A wide clinical spectrum of MERS-CoV infection has been reported ranging from asymptomatic infection to acute upper respiratory illness, and rapidly progressive pneumonitis, respiratory failure, septic shock and multi-organ failure resulting in death. Most MERS-CoV cases have been reported in adults (median age approximately 50 years, male predominance), although children and adults of all ages have been infected (range 0 to 109 years). Most hospitalized MERS-CoV patients have had chronic co-morbidities. Among confirmed MERS-CoV cases reported to date, the case fatality proportion is approximately 35%.
Limited clinical data for MERS-CoV patients are available; most published clinical information to date is from critically ill patients. At hospital admission, common signs and symptoms include fever, chills/rigors, headache, non-productive cough, dyspnea, and myalgia. Other symptoms can include sore throat, coryza, nausea and vomiting, dizziness, sputum production, diarrhea, and abdominal pain. Atypical presentations including mild respiratory illness without fever and diarrheal illness preceding development of pneumonia have been reported. Patients who progress to requiring admission to an intensive care unit (ICU) often have a history of a febrile upper respiratory tract illness with rapid progression to pneumonia within a week of illness onset.
The median incubation period for secondary cases associated with limited human-to-human transmission is approximately 5 days (range 2-14 days). In MERS-CoV patients, the median time from illness onset to hospitalization is approximately 4 days. In critically ill patients, the median time from onset to intensive care unit (ICU) admission is approximately 5 days, and median time from onset to death is approximately 12 days. In one series of 12 ICU patients, the median duration of mechanical ventilation was 16 days, and median ICU length of stay was 30 days, with 58% mortality at 90 days. Radiographic findings may include unilateral or bilateral patchy densities or opacities, interstitial infiltrates, consolidation, and pleural effusions. Rapid progression to acute respiratory failure, acute respiratory distress syndrome (ARDS), refractory hypoxemia, and extrapulmonary complications (acute kidney injury requiring renal replacement therapy, hypotension requiring vasopressors, hepatic inflammation, septic shock) has been reported.
Laboratory findings at admission may include leukopenia, lymphopenia, thrombocytopenia, and elevated lactate dehydrogenase levels. Co-infection with other respiratory viruses and a few cases of co-infection with community-acquired bacteria at admission has been reported; nosocomial bacterial and fungal infections have been reported in mechanically-ventilated patients. MERS-CoV virus can be detected with higher viral load and longer duration in the lower respiratory tract compared to the upper respiratory tract, and has been detected in feces, serum, and urine.
Duration of MERS-CoV shedding in the respiratory tract is typically longer in more severely ill patients than mildly ill patients, and evidence of virus has been detected in survivors for a month or more after onset. Limited data are available on the duration of extrapulmonary MERS-CoV shedding.
No specific treatment for MERS-CoV infection is currently available. Clinical management includes supportive management of complications and implementation of recommended infection prevention and control measures. For more information, see the World Health Organization guidance for clinical management of severe acute respiratory syndrome when MERS-CoV infection is suspected.
For additional information on MERS, see
- Interim Guidance for Health Professionals
- Case Definitions
- Infection Prevention and Control
- Preparedness Checklists and Resources
- Interim Home Care and Isolation Guidance
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