MERS, or Middle East Respiratory Syndrome, is a viral respiratory illness caused by a coronavirus called MERS-CoV. First identified in Saudi Arabia in 2012, it carries a case fatality rate of roughly 35%, making it one of the deadliest coronaviruses known to infect humans. The virus circulates primarily in dromedary camels and occasionally spills over into people, with most cases concentrated in the Arabian Peninsula.
How MERS Spreads
Dromedary camels are the main reservoir for MERS-CoV. People typically catch the virus through direct contact with infected camels or by consuming raw camel products like unpasteurized milk. The virus is currently classified into three clades: clades A and B circulate among camels in the Arabian Peninsula, while clade C is found in camels across Africa.
Human-to-human transmission is possible but inefficient. The virus does not spread easily in everyday community settings, and large-scale community outbreaks have never been documented. Where MERS does amplify is inside hospitals. The largest outbreaks on record have been heavily concentrated in healthcare facilities, with the proportion of hospital-linked cases ranging from about 44% in a 2014 Jeddah outbreak to 100% in outbreaks in Al-Hasa, Saudi Arabia and South Korea. In these settings, “super-spreader” events occur when an unrecognized case exposes other patients and staff before infection control measures kick in. Notably, most secondary MERS cases in hospital outbreaks have been other patients visiting the same facility, rather than healthcare workers.
Symptoms and How Quickly They Appear
After exposure, symptoms typically show up around day five, though the incubation period ranges from 2 to 14 days. The illness can look very different from person to person. Some people have no symptoms at all. Others experience mild cold-like symptoms. And some develop life-threatening pneumonia.
The most common symptoms include:
- Fever
- Shortness of breath
- Dry cough
- Chills
- Headache
- Muscle aches
Some patients also report sore throat, runny nose, dizziness, nausea, vomiting, diarrhea, and abdominal pain. In severe cases, the illness can progress from a mild upper respiratory infection to full-blown pneumonia within a week. From there, it can spiral into respiratory failure, kidney injury, dangerously low blood pressure, liver inflammation, or septic shock. Patients who reach this stage often need mechanical ventilation and intensive care.
Who Faces the Highest Risk
Severe MERS tends to hit hardest in people who already have underlying health conditions. Older adults and those with chronic diseases like diabetes, kidney disease, heart disease, or lung disease are significantly more likely to develop serious complications. People with weakened immune systems are also at elevated risk. Healthy individuals who contract MERS are more likely to have mild or even undetectable symptoms.
Where Cases Have Been Reported
Since 2012, 27 countries have reported MERS cases to the World Health Organization. Saudi Arabia accounts for the vast majority, with over 2,200 confirmed cases. South Korea reported 186 cases, almost all from a single hospital-driven outbreak in 2015. The United Arab Emirates has recorded 94 cases, followed by smaller numbers in Jordan, Qatar, Oman, Iran, Kuwait, and several other countries across the Middle East, North Africa, Europe, and Asia. Cases outside the Arabian Peninsula have almost always been linked to travel from the region.
The WHO continues to track MERS globally, with its most recent data submission as of November 2025.
How MERS Is Diagnosed
Diagnosis relies on a specialized lab test that detects the virus’s genetic material. The CDC recommends collecting three types of specimens: a lower respiratory sample (such as fluid from deep in the lungs or sputum), an upper respiratory sample (swabs from the nose and throat), and a blood sample. All three are needed because the virus may be present in different concentrations at different sites. A positive result from a state or local lab is considered “presumptive” and requires confirmation by the CDC.
Treatment Options
There is no approved antiviral treatment or vaccine for MERS. Care is entirely supportive, meaning doctors focus on keeping patients stable while their immune system fights the infection. For mild cases, that might mean rest, fluids, and monitoring. For severe cases, it means ICU-level support including mechanical ventilation and, in the most critical situations, a machine that oxygenates the blood outside the body (ECMO). One study found that ECMO reduced mortality in severe MERS patients, making it the only intervention with even limited evidence of a life-saving benefit.
Various antiviral drugs have been tried, including combinations of ribavirin with different types of interferon, but none have shown clear effectiveness in humans. Corticosteroids and certain antibiotics have also been studied without demonstrated benefit. Vaccine candidates have reached early-stage clinical trials and shown acceptable safety profiles, but none have advanced to widespread use.
How to Reduce Your Risk
Prevention centers on avoiding the virus at its source. If you are traveling to the Arabian Peninsula or areas where MERS-CoV circulates in camels, the WHO recommends several specific precautions:
- Avoid direct contact with camels, especially if you have diabetes, kidney disease, lung disease, or a weakened immune system.
- Do not drink raw camel milk or camel urine, both of which have been identified as potential routes of infection.
- Cook camel meat thoroughly before eating. Pasteurized camel milk is considered safe.
- Wash your hands frequently before and after visiting farms, markets, barns, or any place where camels are kept.
- Avoid contact with sick animals of any kind.
In healthcare settings, infection control is critical. Droplet precautions (surgical masks), contact precautions (gowns and gloves), and adequate air circulation in treatment rooms all help prevent the hospital-based super-spreading events that have defined the largest MERS outbreaks. Rapid identification and isolation of suspected cases remains the single most effective way to stop a cluster before it grows.