Middle East Respiratory Syndrome
What is it?
Middle East Respiratory Syndrome (MERS) is a respiratory illness caused by a coronavirus called Middle East Respiratory Syndrome Coronavirus (MERS-CoV). This virus belongs to the same family of viruses that causes the common cold, severe acute respiratory syndrome (SARS), and COVID-19.
MERS is a zoonotic disease, meaning it passes from animals to humans. Dromedary camels have been shown to also carry the virus, and are thought to be the main source of infections in humans. Direct or indirect contact with infected dromedary camels, including animal husbandry, care, and slaughter, increases the risk of infection with MERS-CoV. Other risk factors include consumption of raw or undercooked dromedary meat, milk or urine. Human-to-human transmission is possible, but only a few such transmissions have been found among family members living in the same household. In health care settings, however, human-to-human transmission appears to be more frequent.
The origins of the virus are not fully understood but, according to the analysis of different virus genomes, it is believed that it may have originated in bats and was transmitted to camels sometime in the distant past.
Where does it occur?
The first documented cases of MERS-CoV were identified in 2012 in Jordan and Saudi Arabia. Since then, most cases have been reported from the Arabian Peninsula, with Saudi Arabia reporting about 80% of global total cases. From 2012 to 2020, 27 countries have reported cases of MERS to the WHO, of which 12 are in the Eastern Mediterranean WHO region. All reported cases of MERS to date have been linked to the Arabian Peninsula.
In 2015, the Republic of Korea suffered the largest MERS outbreak outside of the Middle East, with 185 laboratory-confirmed cases and 38 deaths reported. The outbreak was caused by the importation of a single case returning from the Arabian Peninsula.
Who does it affect?
MERS-CoV can infect people of any age, however middle-aged adults are at highest risk of infection. The age group 50-59 years has been the most affected by primary infections (i.e. from dromedary camels). The age group 30-39 years is the most affected among secondary cases (acquired from other persons through human-to-human transmission).
The symptoms of disease may vary from case to case, with a clinical spectrum ranging from infection with no symptoms, mild respiratory illness to severe respiratory disease and death. MERS-CoV infection typically causes respiratory symptoms including cough, shortness of breath and pneumonia. Other symptoms include fever, headache, and diarrhoea.
The virus appears to cause more severe disease in older people, people with weakened immune systems, and those with chronic diseases such as renal disease, cancer, chronic lung disease, and diabetes.
Approximately 35% of people with confirmed MERS-CoV infection have died. However, this may be an overestimate of the true case fatality risk (CFR), as mild cases of MERS may be missed by existing surveillance systems.
How do we currently prevent infections?
MERS-CoV, like other coronaviruses, is thought to spread from an infected person’s respiratory secretions, such as through coughing. However, the precise ways the virus spreads are not currently well understood. MERS-CoV has spread from ill people to others through close contact, such as caring for or living with an infected person. Infected people have spread MERS-CoV to others in healthcare settings, such as hospitals.
Adherence to strict infection prevention protocols in health care settings is essential. Preventive measures in the community including hand hygiene, coughing away from others and into elbows, and avoiding social contacts when symptomatic.
When handling camels, practicing good hygiene measures is important, and protective equipment may be advised in some instances.
When handling camel products, raw materials should be handled according to safe food hygiene practices, and consumption of raw and undercooked meat and milk should be avoided.
No vaccine or specific treatment is currently available, however several MERS-CoV specific vaccines and treatments are in development. Treatment is supportive and based on the patient’s clinical condition.
How is CEPI supporting MERS vaccine R&D?
CEPI has invested in the development of four MERS vaccine candidates, three of which are in active development. Three of these vaccines have entered clinical trials.
With partnerships initiated to advance development of MERS vaccine candidates, CEPI was able to use this knowledge of another coronavirus and act quickly in response to the COVID-19 pandemic.
In October 2020, the first WHO International Standard for MERS-CoV antibodies was established by the WHO Expert Committee on Biological Standardization. This standard was developed by the International Vaccine Institute (IVI) and the National Institute for Biological Standards and Control (NIBSC), funded and facilitated by CEPI. Antibody standards act as a comparator to assess the antibody (immune) response elicited by candidate vaccines. It is also a useful tool for research on MERS-CoV immunity.