MERS‑CoV is the coronavirus responsible for Middle East respiratory syndrome, an acute respiratory disease first reported in Saudi Arabia in 2012. This enveloped, positive‑sense RNA virus belongs to the Betacoronavirus genus and lineage C.
Pathogenesis and Virology
MERS‑CoV is an enveloped virus with a single‑stranded positive‑sense RNA genome around 30 kb. It is a lineage C betacoronavirus, related to bat coronaviruses. The virion is roughly 80–120 nm in diameter with a lipid envelope containing spike glycoproteins. Unlike SARS‑CoV, MERS‑CoV uses dipeptidyl peptidase 4 (DPP4, also known as CD26) as its cellular receptor, found on epithelial cells of the lower respiratory tract and on certain immune cells. Binding to DPP4 triggers membrane fusion and entry. Following entry, the virus replicates in the cytoplasm using a replication–transcription complex derived from translated polyproteins; assembly occurs in the endoplasmic reticulum–Golgi intermediate compartment. Genomic analyses suggest a bat origin; however, dromedary camels are the primary reservoir and source of human infections. The virus causes a severe respiratory illness characterized by fever, cough, shortness of breath and frequently pneumonia; some patients develop acute kidney injury and gastrointestinal symptoms. The immune response includes a strong interferon reaction but also evidence of immune evasion through suppression of innate signaling. MERS CoV has a higher case fatality rate (about 34%) than SARS CoV and SARS CoV 2, particularly in older adults and those with comorbidities.
Significant Outbreaks and Observations
Middle East respiratory syndrome was first recognized in a patient from Jeddah, Saudi Arabia, in June 2012, and subsequent cases were linked to healthcare‑associated transmission and contact with camels. As of early 2025, the World Health Organization has recorded around 2,600 laboratory‑confirmed cases and nearly 900 deaths across 27 countries, with most cases occurring in Saudi Arabia. The largest outbreak outside the Arabian Peninsula occurred in South Korea in 2015, resulting in 186 cases and 38 deaths, all traced to a single traveller returning from the Middle East. Sustained human‑to‑human transmission is uncommon, but nosocomial clusters highlight the importance of infection control measures. MERS‑CoV continues to circulate in camels across the Middle East, Africa and parts of Asia, posing an ongoing risk of zoonotic spillover. Surveillance of camel populations and public health education about avoiding contact with camel secretions are key preventive strategies.
MERS CoV remains a lineage C betacoronavirus that occasionally spills over from dromedary camels into humans, causing severe respiratory illness with a high case fatality. While human‑to‑human transmission is limited, healthcare‑associated outbreaks emphasize the need for vigilance and rapid containment. Understanding the virus’s ecology, receptor usage and pathogenesis informs current surveillance and future therapeutic or vaccine development.
Related Terms: SARS‑CoV, SARS CoV 2, Camel, Betacoronavirus, DPP4 receptor