Middle East Respiratory Syndrome: Symptoms, Types, Causes and Treatment

Middle East Respiratory Syndrome (MERS) is a viral respiratory illness that has reshaped global awareness around coronaviruses and zoonotic diseases. Since its emergence in 2012, it has challenged healthcare systems with its severe symptoms, high mortality rate, and complex transmission patterns. This article provides a comprehensive and engaging overview of MERS, focusing on its symptoms, types, causes, and current approaches to treatment—each supported by evidence from recent scientific studies.

Symptoms of Middle East Respiratory Syndrome

MERS can range from a mild, cold-like illness to severe, life-threatening respiratory failure. Recognizing the spectrum of symptoms is crucial for early detection, effective isolation, and optimizing patient outcomes.

Common Symptom	Frequency/Details	Severity Range	Source
Fever	Nearly all cases	Mild to severe	1 2 3 5
Cough	Majority of patients	Mild to severe	1 2 3 5
Shortness of breath	Frequently reported	Often severe	1 2 3 5
Pneumonia	Common but not universal	Often severe	3 5 7
Gastrointestinal	Diarrhea, vomiting, abdominal pain	Variable	1 2 5
Myalgia	Muscle aches, less common	Usually mild	1 3
Radiographic changes	Abnormal chest X-ray in all patients	Extensive range	1 2 7
Asymptomatic cases	Described, especially in the young	Mild	4 8

Table 1: Key Symptoms

The Symptom Spectrum

MERS most often presents with fever, cough, and shortness of breath. Fever is nearly universal, sometimes accompanied by chills or rigors. Cough and dyspnea are also frequent, with many patients progressing to pneumonia or acute respiratory distress syndrome (ARDS) 1 2 3 5.

• Pneumonia is detected in most hospitalized patients, but it is not always present at the time of admission 3 5.
• Gastrointestinal symptoms—including diarrhea, vomiting, and abdominal pain—are reported in over a quarter of cases, underscoring that MERS is not solely a respiratory illness 1 2 5.
• Myalgia (muscle aches) and general malaise may occur, but are less prominent 1 3.
• Radiographic abnormalities are seen in all hospitalized cases, ranging from subtle infiltrates to widespread bilateral changes 1 2 7.

Severe and Atypical Presentations

Most severe presentations occur in older adults and those with underlying health conditions, especially diabetes, chronic kidney disease, and cardiovascular disease 1 3 4 7 9. In these groups, the infection can progress rapidly to respiratory failure, requiring intensive care and mechanical ventilation. Non-respiratory organ failure and multi-organ involvement are not uncommon in critical cases 7.

Asymptomatic and Mild Cases

While the majority of cases present with respiratory symptoms, asymptomatic infections have been identified, particularly in younger or healthier individuals and among contacts of confirmed cases 4 8. This wide range in clinical severity complicates detection and infection control.

Types of Middle East Respiratory Syndrome

The clinical and epidemiological landscape of MERS is shaped by where and how infection occurs, as well as by the severity of disease. Understanding these “types” helps with risk assessment and public health interventions.

Type	Description	Key Features	Source
Primary infection	Direct zoonotic (animal-to-human) exposure	Often sporadic	4 5 9 10
Secondary infection	Human-to-human, close contact	Clusters, outbreaks	2 4 5 10
Healthcare-associated	Transmission in hospitals/clinics	Nosocomial outbreaks	2 3 7 10
Mild/asymptomatic	Little/no symptoms	Young/healthy people	4 8
Severe/critical	Severe respiratory & multi-organ failure	ICU, high mortality	3 4 7 9

Table 2: Clinical and Epidemiological Types

Primary vs. Secondary Infection

Primary MERS-CoV infections are thought to arise from direct or indirect contact with infected dromedary camels, the main animal reservoir. These cases often occur sporadically in the community 4 5 9 10.

Secondary infections result from human-to-human transmission, typically through close contact with symptomatic or, less commonly, asymptomatic individuals 4 5 10. This type is responsible for clusters within families or among health care workers.

Healthcare-Associated (Nosocomial) Infections

A hallmark of MERS epidemiology is its propensity for hospital outbreaks. Transmission often occurs in dialysis units, intensive care units, and other hospital settings where close interactions and aerosol-generating procedures are common 2 3 7 10. These outbreaks can involve both patients and healthcare workers, amplifying the impact.

Mild, Asymptomatic, and Severe Cases

Clinical severity varies widely:

• Mild or asymptomatic cases are more likely in younger, healthy people, and may go undetected without targeted testing 4 8.
• Severe and critical cases are characterized by pneumonia, ARDS, non-respiratory organ failure, and high mortality, especially in elderly patients or those with comorbidities 3 4 7 9.

Causes of Middle East Respiratory Syndrome

MERS is a zoonotic disease—originating in animals and crossing over into humans. Understanding the causes and transmission pathways is key to controlling its spread.

Cause/Source	Role in Transmission	Notable Facts	Source
MERS-CoV virus	Direct cause	Novel betacoronavirus	4 5 6 8 9
Dromedary camels	Animal reservoir, zoonotic source	Shed virus, close contact risk	4 5 9 10
Human-to-human	Secondary transmission, esp. in hospitals	Requires close contact	2 4 5 10
Environmental/unknown	Precise route unclear in many cases	Research ongoing	4 5 10

Table 3: Causes and Transmission

The MERS Coronavirus (MERS-CoV)

MERS is caused by the Middle East respiratory syndrome coronavirus, a single-stranded RNA virus belonging to the betacoronavirus genus 4 5 6 8 9. It is genetically related to coronaviruses found in bats, but dromedary camels are the main recognized animal reservoir for human infection.

Zoonotic Origin: The Role of Camels

• Dromedary camels are widely implicated as the animal source, with evidence of viral shedding and seropositivity in camels across the Middle East 4 5 9 10.
• Human infections have been linked to direct or indirect contact with camels, but the exact mechanisms remain unclear. Routes may include respiratory droplets, contaminated surfaces, or consumption of raw camel products 4 9 10.
• Not all cases report camel exposure, suggesting other environmental or animal vectors may exist.

Human-to-Human Transmission

• Secondary transmission occurs mainly through close contact, particularly in healthcare settings (e.g., providing unprotected care, aerosol-generating procedures) 2 4 5 10.
• Transmission in the wider community appears limited, with most human-to-human spread associated with outbreaks in hospitals or among close household contacts 2 5 10.

Other Transmission Factors

• The virus does not seem to spread easily without close or prolonged contact.
• Super-spreading events in hospitals, often due to delayed recognition and inadequate infection control, have caused significant outbreaks 2 3 10.
• The potential for increased transmissibility through viral mutation remains a public health concern 4.

Treatment of Middle East Respiratory Syndrome

Despite years of research, there is no specific antiviral treatment approved for MERS. Management focuses on supportive care and, in severe cases, advanced organ support.

Treatment Approach	Details/Examples	Effectiveness/Status	Source
Supportive care	Oxygen, ventilation, fluids, ICU	Mainstay, improves outcome	7 8 9
Antivirals (investigational)	Remdesivir, lopinavir/ritonavir, interferons	Some show promise in studies	11 13 14 15
Corticosteroids	Used in severe/critical cases	May delay viral clearance	12
Ribavirin/interferon	Used off-label in some cases	No clear mortality benefit	15
Infection control	Isolation, PPE, hygiene in hospitals	Critical for prevention	2 4 5 8 10

Table 4: Treatment Approaches

Supportive Care

The cornerstone of MERS treatment is supportive care:

• Oxygen supplementation, mechanical ventilation, and extracorporeal membrane oxygenation (ECMO) may be needed for severe hypoxemia 7 9.
• Management of organ failure (e.g., renal replacement therapy for kidney injury) is often required in critically ill patients 7.

Antiviral and Immunomodulatory Therapies

Several antiviral agents have been tested, mainly in laboratory or animal studies:

• Remdesivir has shown potent activity against MERS-CoV in vitro and in animal models, reducing virus replication and lung damage. It is considered a promising candidate for clinical trials, though not yet approved for MERS 11 13.
• Lopinavir/ritonavir with interferon beta has been used in human cases, with mixed results; remdesivir appears superior in preclinical studies 11.
• Ribavirin and interferons have been used off-label, particularly in Saudi Arabia. Large clinical studies have not demonstrated a reduction in mortality or faster viral clearance with these agents 15.

Corticosteroids

• Corticosteroids are sometimes used for critically ill patients, but recent studies indicate they do not reduce mortality and may prolong the time required to clear the virus 12. Their use should be carefully considered, balancing potential benefits and risks.

Other Therapies and Drug Repurposing

• Investigations into repurposing existing drugs (e.g., cancer therapeutics, antipsychotics) have identified candidates with antiviral activity against MERS-CoV in the lab, but these require further in vivo and clinical evaluation before they can be recommended 14.

Infection Prevention and Control

• Strict infection control measures in hospitals—such as isolation of suspected cases, use of personal protective equipment (PPE), and hand hygiene—are essential to prevent nosocomial transmission 2 4 5 8 10.
• There is ongoing research into the development of vaccines for camels and potentially humans, but none are currently available 9.

Conclusion

Middle East Respiratory Syndrome remains a formidable challenge due to its high mortality, unpredictable outbreaks, and lack of specific treatments. Understanding its symptoms, types, causes, and management strategies is essential for both healthcare providers and the public.

Key Points:

• Symptoms range from mild flu-like illness to severe pneumonia and multi-organ failure, especially in older adults with comorbidities.
• Types include primary (animal-to-human), secondary (human-to-human), healthcare-associated, and a spectrum from asymptomatic to critical illness.
• Causes center on a novel coronavirus (MERS-CoV), with dromedary camels as the primary reservoir and hospitals as key sites for human-to-human spread.
• Treatment relies mainly on supportive care; while antiviral options like remdesivir show promise in preclinical studies, no specific therapy is yet approved. Rigorous infection control is the cornerstone of outbreak prevention.

As MERS continues to pose a global health risk, ongoing research, vigilant surveillance, and public health readiness are vital to mitigate its impact and prepare for future emerging coronaviruses.