Middle East respiratory syndrome (MERS)

Middle East respiratory syndrome (MERS) is a zoonotic disease and was first identified in Saudi Arabia in 2012, with 27 countries now having reported cases. Approximately 35 per cent of MERS-Coronavirus (MERS-CoV) infection cases are fatal. This may, however, be an overestimate of the true mortality rate, as mild cases may be missed by existing surveillance systems. Until more is known about the disease, the case fatality rates are counted only amongst the laboratory-confirmed cases.

The following are standard case definitions to allow national health authorities to interpret data in an international context. However, during an outbreak case definitions may be adapted to the local context and the Red Cross Red Crescent should use those agreed/established by national health authorities. NB: Consider that during community-based surveillance, volunteers should use broad (simplified) case definitions (referred to as community case definitions) to recognize most or all possible cases, provide relevant risk communication and appropriate actions and encourage them to seek care. Other actors such as healthcare workers or investigators studying the cause of a disease, on the other hand, can use more specific case definitions that may require laboratory confirmation.

Probable case

Definition 1: A febrile acute respiratory illness with clinical, radiological or histopathological evidence of pulmonary parenchymal disease (e.g. pneumonia or acute respiratory distress syndrome (ARDS)) AND direct epidemiologic link with a laboratory-confirmed MERS-CoV case AND testing for MERS-CoV is unavailable, negative on a single inadequate specimen or inconclusive.

Definition 2: A febrile acute respiratory illness with clinical, radiological or histopathological evidence of pulmonary parenchymal disease (e.g. pneumonia or ARDS) that cannot be explained fully by any other aetiology AND the person resides in or has travelled in the Middle East, or in countries where MERS-CoV is known to be circulating in dromedary camels or where human infections have recently occurred; AND testing for MERS-CoV is inconclusive.

Definition 3: An acute febrile respiratory illness of any severity AND direct epidemiologic link with a confirmed MERS-CoV Case AND testing for MERS-CoV is inconclusive.

Confirmed case: A person with laboratory confirmation of MERS-CoV infection, irrespective of clinical signs and symptoms.

WHO case definition source of information: https://www.who.int/csr/disease/coronavirus_infections/mers-interim-case-definition.pdf?ua=1

• People with close exposure to camels, like traders or those who use camels as a means of transport.
• Lack of appropriate sanitation and hygiene measures.
• Close contacts to cases of MERS, e.g. working as a caregiver.
• Refugees, internally displaced people and migrants in outbreak regions are at increased risk to become infected.
• Health personnel not using recommended infection control precautions.

Attack rates will vary from one outbreak to another. In case of an outbreak, consult the latest information provided by health authorities.

Secondary attack rate among household contacts: 0.4 per cent to 15.8 per cent.

To date it is difficult to provide an attack rate in a rare disease with low numbers of known cases.

• Elderly
• People with weakened immune systems.
• Immunosuppressed persons such as those receiving chemotherapy,  transplant recipients or HIV carriers.
• People with chronic diseases such as renal disease, cancer, chronic lung or liver disease, and diabetes.

Middle East Respiratory Syndrome Coronavirus (MERS-CoV).

Zoonotic disease: Dromedary camels.

• Zoonotic disease: the route of transmission from animals to humans is not fully understood, but dromedary camels are a major reservoir host for MERS-CoV and an animal source of infection in humans.
• Contact transmission: the virus does not pass easily from person to person unless there is close contact, such as providing unprotected care to an infected patient. Few human-to-human transmissions have been identified among family members, patients and healthcare workers.

2—14 days.

The duration of infectivity for MERS-CoV infection is unknown. While standard precautions should always be applied, additional barrier precautions should be used for the duration of symptomatic illness and continued for 24 hours after the resolution of symptoms.

• The clinical spectrum of MERS-CoV infection ranges from no symptoms (asymptomatic) or mild respiratory symptoms to severe acute respiratory disease and death.
• A typical presentation of MERS-CoV disease is fever, cough and shortness of breath. Pneumonia is a common finding, but not always present.
• Gastrointestinal symptoms, including diarrhoea, have also been reported.
• Severe illness can cause respiratory failure that requires mechanical ventilation and support in an intensive care unit and multi-organ failure.

Common cold, influenza, avian influenza, severe acute respiratory syndrome (SARS), pneumonia, respiratory syncytial virus (RSV) infection, COVID-19 disease.

• Real time polymerase chain reaction (PCR).
• Serology testing (for surveillance purpose only).

Please refer to the appropriate local or international guidelines for clinical management. All clinical management including the administration of any treatment should be conducted by health professionals.

• No vaccine or specific treatment is currently available. Treatment is supportive and based on the patient’s clinical condition.
• Isolation of suspected cases is necessary.

It is not clearly understood whether a naturally acquired immunity provides a lifelong protection from reinfection.