Open Outbreak

Middle East respiratory syndrome

Also known as: MERS, MERS-CoV, Middle East respiratory syndrome coronavirus

Middle East respiratory syndrome, or MERS, is a serious infection caused by a coronavirus called MERS-CoV. WHO says people are infected through direct or indirect contact with dromedary camels, which are the natural host and main animal source. The virus can also spread from person to person, but WHO describes this as limited and usually not sustained; it has happened mainly among close contacts and in health-care settings. Illness ranges from mild or even no symptoms to severe pneumonia and death. WHO notes that reported deaths are high, but the reported fatality rate likely overstates the true risk because mild cases can be missed. People with diabetes, kidney failure, chronic lung disease, or weakened immune systems appear to be at higher risk of severe disease. As of the WHO materials returned here, there is no specific proven antiviral treatment and no licensed human vaccine. Prevention relies on infection control in hospitals and reducing risky camel exposures, including avoiding raw camel milk.

Key facts

TransmissionDirect or indirect contact with dromedary camels; limited, non-sustained person-to-person spread, mainly among close contacts and in health-care settings.
Incubationunknown
Case fatalityApproximately 35% of reported laboratory-confirmed patients have died, according to WHO; WHO says this may overestimate the true mortality rate because mild cases may be missed.
Reproduction numberunknown
VaccineNo licensed human vaccine identified in the WHO and literature sources returned in this session.
TreatmentNo specific proven treatment identified in the WHO and literature sources returned in this session; care is mainly supportive.
ReservoirDromedary camels are the natural host and zoonotic source according to WHO.
Endemic regionsPrimarily the Middle East where MERS-CoV circulates in dromedary camels, especially countries on the Arabian Peninsula; exported cases have occurred elsewhere.

Transmission

WHO says most human MERS infections start with direct or indirect contact with dromedary camels, the main animal source. Reported exposures include close contact with camels and use of camel products such as raw milk. The virus can also pass from person to person, but WHO describes this spread as limited and not sustained over long chains. Most documented human-to-human spread has happened among close contacts and in health-care settings, where patients may be very ill and where early symptoms can look like other respiratory infections. That matters because staff may not recognize a case right away unless they use routine infection-control measures for all patients with respiratory symptoms. WHO continues to expect occasional new cases in the Middle East and occasional exported cases to other countries after travel or other exposure. The available sources returned here do not give a firm single reproduction number, so that remains uncertain on this page.

Symptoms and severity

MERS is mainly a respiratory illness, but it does not look the same in every person. The overview source says symptoms can range from none, to mild illness, to severe disease. Typical symptoms include fever, cough, shortness of breath, and sometimes diarrhea. WHO notes that early symptoms are non-specific, meaning they can look like many other infections at first. Some patients worsen and develop severe pneumonia or require intensive care. WHO also says MERS appears to cause more severe disease in people with diabetes, kidney failure, chronic lung disease, or weakened immune systems. Severity is high enough that WHO repeatedly describes the disease as causing high mortality. In the WHO outbreak materials returned here, the commonly cited figure is that about 35% of reported laboratory-confirmed patients have died. WHO warns this may overestimate the true death rate because mild cases may not be detected by surveillance systems.

Treatment and vaccines

The sources returned here do not identify a licensed human vaccine for MERS, and they do not point to a specific treatment with proven efficacy in routine care. That means management is mainly supportive: oxygen, careful monitoring, and intensive care when needed. WHO outbreak notices focus strongly on early identification, isolation, and infection prevention in hospitals, because stopping spread in health-care settings is one of the most important tools available. WHO advises standard precautions for all patients, plus added droplet, contact, eye, and airborne precautions in the situations it describes. For the public, prevention also means reducing risky camel exposures in places where the virus circulates, especially avoiding raw camel milk and practicing good hand and food hygiene. The literature results returned in this session discuss the need for vaccines and therapeutics, but the snippets provided do not show any approved product for general use. On that basis, this page treats vaccine availability and specific antiviral treatment as not established.

Where it occurs

MERS was first recognized in 2012 and remains centered in and around the Arabian Peninsula, where WHO says MERS-CoV circulates in dromedary camels. Saudi Arabia has reported the largest share of cases in the WHO notices returned here, but recent WHO items also involve Qatar, Oman, and the United Arab Emirates. Cases have also been exported to other countries after travel or other exposure, with WHO archive entries in the tool results including the Republic of Korea, the United Kingdom, Malaysia, Thailand, Austria, Bahrain, and Lebanon. Exported cases do not mean the virus is established in those places; they usually reflect travel-associated infection or limited secondary spread. The practical message is that geography is linked more to infected camels and travel connections than to stable global circulation in humans. For most readers, the main risk settings remain camel exposure in affected regions and health-care settings where an infected patient is being treated.

Recent history

MERS has been a recurring but usually low-number event in WHO reporting rather than a constantly expanding global epidemic. This site’s archive count provided with the request is 65 WHO-linked or major events since 1996. In the WHO item covering early 2021, WHO said that from 2012 to 2021-03-11 there had been 2,574 laboratory-confirmed cases and 886 associated deaths reported globally. More recent WHO notices in the returned archive show continued sporadic reporting: Saudi Arabia reported nine cases in 2023, the United Arab Emirates reported one case in 2023, Oman reported one case in 2023, Qatar reported two cases including one death in 2022, and Saudi Arabia reported several updates in 2021 and 2022. WHO’s overall assessment in these notices is consistent: additional cases are expected from the Middle East, and exported cases may continue, but the updates cited did not change the overall global risk assessment.

What to watch

Several signals would make MERS more concerning. The first is a clear change in transmission: WHO currently describes person-to-person spread as limited and non-sustained, mostly in close contacts and health-care settings. Evidence of efficient spread in the community, without camel exposure, would be a major warning sign. The second is geography. WHO expects more cases in the Middle East and occasional exported cases; repeated outbreaks in new regions without obvious importation would matter. The third is hospital spread. Large clusters in clinics or hospitals would suggest gaps in infection prevention or a change in how easily the virus spreads. The fourth is severity or treatment failure: more cases in younger or previously healthy people, or signs that supportive care is becoming less effective, would raise concern. Finally, watch vaccine and countermeasure progress. The returned sources do not show a licensed human vaccine or specific proven therapy, so limited medical tools remain a vulnerability if case numbers rise.

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