Middle East respiratory syndrome

Middle East respiratory syndrome
Name	Middle East respiratory syndrome
Field	Infectious disease, Pulmonology
Symptoms	Fever, cough, shortness of breath
Complications	Pneumonia, Kidney failure
Causes	MERS coronavirus (MERS-CoV)
Risks	Contact with dromedary camels, healthcare exposure
Diagnosis	PCR testing
Differential	Influenza, SARS, other viral pneumonia
Prevention	Hand hygiene, avoiding contact with camels
Treatment	Supportive care
Frequency	~2600 cases as of 2023
Deaths	~935 deaths as of 2023

Middle East respiratory syndrome. It is a viral respiratory infection caused by the MERS coronavirus (MERS-CoV). First identified in 2012 in Saudi Arabia, the disease has led to outbreaks primarily in the Arabian Peninsula but also through travel to other regions including South Korea. The virus is considered a threat to global health security by the World Health Organization.

Signs and symptoms

The clinical presentation ranges from asymptomatic infection to severe pneumonia and multi-organ failure. Common initial symptoms include fever, non-productive cough, and shortness of breath. Gastrointestinal symptoms such as diarrhea and nausea are also frequently reported. Severe cases often progress rapidly to acute respiratory distress syndrome (ARDS), requiring mechanical ventilation and intensive care unit support. Complications can include septic shock, acute kidney injury, and pericarditis. The incubation period is typically five to six days but can range from two to fourteen days.

Cause

The disease is caused by the MERS coronavirus, a betacoronavirus of lineage C. The virus is zoonotic, with dromedary camels serving as the primary reservoir host and source of human infection. Genetic analyses show that circulating viruses in camels in regions like Saudi Arabia, Qatar, and Egypt are nearly identical to strains found in human cases. The virus enters host cells by binding to the dipeptidyl peptidase-4 (DPP4) receptor, which is abundantly expressed in the human lower respiratory tract. Human-to-human transmission occurs primarily in healthcare settings and among close family contacts, often through droplet transmission.

Diagnosis

Definitive diagnosis requires laboratory testing on respiratory specimens such as bronchoalveolar lavage fluid or sputum. The primary confirmatory test is reverse transcription polymerase chain reaction (RT-PCR) assay targeting specific genes like the upstream of E gene (upE) and the ORF1a gene. Serological tests like enzyme-linked immunosorbent assay (ELISA) and immunofluorescence assay can detect antibodies but are mainly used for epidemiological studies. Differential diagnosis must rule out other respiratory pathogens such as influenza virus, respiratory syncytial virus, and bacteria causing community-acquired pneumonia. The Centers for Disease Control and Prevention and the World Health Organization provide case definitions and testing protocols.

Prevention

No licensed vaccine exists. Prevention focuses on standard infection control practices, especially in hospitals. Key measures include hand hygiene using alcohol-based hand rub, wearing personal protective equipment like gowns and N95 respirators, and isolating suspected cases. The World Health Organization advises people with comorbidities like diabetes or chronic lung disease to avoid contact with dromedary camels in affected regions and to refrain from consuming raw camel milk or urine. During the 2015 outbreak in South Korea, extensive contact tracing and quarantine were critical to containment. International travel guidelines are issued by agencies like the European Centre for Disease Prevention and Control.

Treatment

Management is primarily supportive care as no specific antiviral drug is proven effective. Hospitalized patients often require oxygen therapy and mechanical ventilation. Extracorporeal membrane oxygenation (ECMO) has been used in cases of severe respiratory failure. Several agents, including ribavirin combined with interferon-alpha, lopinavir/ritonavir, and remdesivir, have been used empirically based on in vitro activity or experience with related coronaviruses like SARS-CoV, but robust clinical trial data from randomized controlled trials are lacking. Care for complications such as renal replacement therapy for kidney failure is often necessary.

Epidemiology

Since its identification in 2012, approximately 2600 laboratory-confirmed cases have been reported to the World Health Organization as of 2023, with about 935 associated deaths, yielding a high case fatality rate near 35%. The majority of cases have occurred in Saudi Arabia, with other cases reported across the Middle East in countries like Jordan, United Arab Emirates, and Oman. Large outbreaks outside the region have been driven by travel, most notably the 2015 outbreak in South Korea linked to a traveler returning from the Arabian Peninsula, which resulted in 186 cases. The virus is considered endemic in dromedary camel populations across East Africa and the Middle East. Surveillance is coordinated by the World Health Organization under the International Health Regulations.

Category:Infectious diseases Category:Viral respiratory tract infections Category:Zoonoses