Blog | Thursday, June 19, 2014

MERS: a primer

The CDC reported the first case of Middle East Respiratory Syndrome (MERS) in the United States. The patient is a health care worker who flew from Saudi Arabia to Chicago (via London), and then traveled by bus to Indiana, where he is currently hospitalized.

I suspect this is the first of many posts on this topic. In case you have not been following the MERS story, I put together a summary to get you up to speed.

• Approximately 400 cases have been reported since the first case was reported in 2012.
• All cases have been acquired in 6 countries in the Arabian peninsula, though some cases became symptomatic after travel to other countries.
• The virus (a novel coronavirus) appears to have originated in bats, but antibodies to the virus have been found in camels.
• Transmission dynamics are not completely understood. Human-to-human transmission does occur, and some cases are associated with contact with camels.
• About 1 in 5 cases have been healthcare workers who cared for patients with MERS.

Clinical (excellent reference by Hui et al here)
• The incubation period is 2-13 days (median, 5 days).
• The illness is characterized by pneumonia, which in most cases is severe (80% require ventilatory support).
• Typical cases begin with fever, cough, chills, sore throat, myalgia and arthralgia, followed by dyspnea and rapid progression to pneumonia.
• Severe cases may be associated with ARDS, septic shock and multiorgan failure.
• Fever is almost always present.
• GI symptoms (nausea, vomiting, or diarrhea) are present in 1/3.
• Chest imaging is always abnormal; findings include bilateral hilar infiltrates, patchy infiltrates, segmental or lobar opacities, ground glass opacities and small pleural effusions.
• Routine laboratory abnormalities are variable.
• Mortality rate is ~30%. In fatal cases, median time from presentation to death is 11.5 days.
• Asymptomatic infection can occur.

Diagnostic Testing (detailed instructions by CDC here)
• In the US, all testing is performed by public health laboratories.
• PCR is available for BAL fluid, tracheal aspirate, pleural fluid, sputum, NP/OP swabs, NP wash/aspirate, and serum.
• Antibody testing: acute (first week of illness), convalescent (≥3 weeks after acute sample obtained).

• No specific antiviral therapy is currently available.
• Treatment is focused on supportive care.

Infection Control and Prevention (CDC guidance here)
• Contact and airborne precautions are indicated for patients under investigation, and suspected and confirmed cases (see CDC case definitions here).
• Eye protection (goggles or face shield) is specifically recommended.
• At this time, there is no available vaccine or chemoprophylaxis.

Michael B. Edmond, MD, FACP, is a hospital epidemiologist in Richmond, Va., with a focus on understanding why infections occur in the hospital and ways to prevent these infections, and sees patients in the inpatient and outpatient settings. This post originally appeared at the blog Controversies in Hospital Infection Prevention.