Clinical Overview of MERS

Clinical presentation

Middle East Respiratory Syndrome (MERS) is caused by Middle East respiratory syndrome coronavirus (MERS-CoV) virus. A wide spectrum of clinical illness in patients with MERS has been reported. People with MERS-CoV infection range from being asymptomatic to having severe acute respiratory illness that may result in death. Most reported MERS cases have had more severe illness, like pneumonia. However, milder cases may be underreported.

Although MERS cases have been reported among children and adults of all ages, older adults account for most MERS cases reported. Among global cases reported to date, 35% of MERS cases resulted in death.

Symptoms

Common signs and symptoms of MERS include:

• fever
• dyspnea (shortness of breath)
• non-productive cough
• chills/rigors
• headache
• myalgia (muscle pain)

Other signs and symptoms can include sore throat, coryza (runny nose and/or sneezing), productive cough, dizziness, nausea and vomiting, diarrhea, and abdominal pain.

MERS patients may have rapid progression from febrile upper respiratory tract illness to pneumonia (i.e., within a week of onset), and some may require intensive care unit (ICU) admission.

Laboratory Findings

Laboratory findings at admission can vary, but can include leukopenia, lymphopenia, thrombocytopenia, and elevated lactate dehydrogenase levels. Other respiratory viruses and community-acquired bacteria have been reported to co-infect patients at the time of hospital admission.

Public health laboratories or CDC can detect MERS-CoV with a targeted polymerase chain reaction (PCR) test. Respiratory specimens are required for testing. Specimens from the lower respiratory tract have a higher sensitivity for detection compared with specimens from the upper respiratory tract.

Duration of MERS-CoV shedding in the respiratory tract is typically longer in more severely ill patients than mildly ill patients. It has been reported that evidence of MERS-CoV RNA has been detected in survivors for a month or more after onset, and culturable virus has been detected up to 25 days after onset, and culturable virus has been detected up to 25 days after onset. Limited data are available on the duration of extrapulmonary MERS-CoV shedding.

Radiographic Findings

Chest radiographic (or other imaging) findings might include unilateral or bilateral patchy densities or opacities, interstitial infiltrates, consolidation, or pleural effusions consistent with pneumonia or acute respiratory distress syndrome (ARDS).

Incubation period

Most patients develop symptoms approximately 5 days after an exposure to an infected person or camel, but the incubation period can range from 2-14 days.

Progression

MERS patients who exhibit rapid progression to pneumonia (i.e., within a week of illness onset) may require admission to an intensive care unit (ICU). Rapid, progressive pneumonitis, acute respiratory distress syndrome (ARDS), refractory hypoxemia, respiratory failure, and extrapulmonary complications, including acute kidney injury, hypotension, hepatitis, and septic shock have been reported.

In hospitalized MERS patients, the median time from the onset of symptoms to a person's hospitalization is approximately 4 days.

In critically ill patients, the median time from onset to ICU admission is approximately 5 days, and median time from onset to death is approximately 12 days.

Complications

Most hospitalized MERS patients have had pre-existing medical conditions that likely increased their risk for severe illness.

Complications of severe MERS have been reported, including rapid progressive pneumonitis, refractory hypoxemia, respiratory failure, and extrapulmonary complications, including acute kidney injury, hypotension, hepatitis, and septic shock.

Patient management

There is currently no specific antiviral treatment for MERS. Clinical management includes supportive management of signs, symptoms, and complications. Implementation of recommended infection prevention and control measures is very important to help prevent the spread of the virus.