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Update November 2013 - Questions and Answers MERS coronavirus (CoV)

What is MERS CoV?
MERS CoV is a particular strain of coronavirus which is thought to cause Middle East Respiratory Syndrome (MERS), a respiratory disease of humans. MERS CoV had not been seen in humans before September 2012. Since then sporadic outbreaks of MERS CoV with human cases have been detected in 9 countries.
According to a recent WHO report, from September 2012 to November 2013, a total of 153 laboratory-confirmed cases of infection with MERS-CoV have been reported, including 64 deaths.     

What are coronaviruses?
Coronaviruses are species of RNA (ribonucleic acid) viruses. They are called coronaviruses because under an electron microscope the virus appears to have a characteristic crown or halo around it. There are many species and strains of coronavirus which have different characteristics, causing a range of signs - from mild to severe disease – in humans and in different animal species. Several different species of coronavirus infect both animals and humans. 

What is the source of MERS CoV?
OIE together with its partner organizations the World Health Organization (WHO), the Food and Agriculture Organization (FAO) and national animal health authorities of affected countries is closely following investigations into a possible animal source of MERS CoV.
The current epidemiological investigation includes researching potential sources of exposure to the virus which are numerous and include other humans, the environment, food and water, as well as animals. Detailed information collected from relatives and other persons in contact with people infected with MERS CoV can help to provide important clues about the source of their infection.
To date, no formal proof has been highlighted on a potential animal origin. Exposure sources and modes of transmission also remain to be clarified.

Can animals become infected with MERS CoV?
Although experimental infection of animal cultured cells and recently monkeys with MERS CoV has been possible, to date the MERS CoV has not been naturally detected in animals.

Are animals responsible for MERS CoV infections in people?
To date there is no evidence that people have become infected through contact with animals. However there is also a possibility that MERS CoV may have evolved from other coronaviruses that have been circulating in certain animals. Additional public health investigations are needed to establish the source of exposure for human infections with MERS CoV when the source has not been identified as another human. So far, three patterns of infection have been reported by WHO: 

  • community acquired cases (the exposure sources remains unknown and might include an animal, food or environmental source)
  • hospital acquired infections
  • infection acquired through close human to human contact (household).


Did MERS CoV come from bats? 
Although a relative to this virus had already been detected in bat species, and a fragment of viral genetic material matching the MERS CoV was recently found in one bat from Saudi Arabia, more evidence is needed to directly link the MERS CoV to bats or any other animal species.

What about the suspicion that camels play a role in MERS?
Currently there is no strong evidence to consider that camels are a source of infection for human cases of MERS. Based on available epidemiological data it is difficult to explain the relationship between positive serological results in camels and cases of human infections with MERS CoV. Indeed, to date, there is no potential similarity between the strain of MERS CoV isolated in humans and the suspicions shown in camels. It is important to remain open minded about all potential sources of exposure for human cases until more information is available.

What about serological tests in animals?
Serology tests aim to detect antibodies produced by the animal against the virus, and not to search for the presence of the virus itself. Often it is difficult and sometimes impossible to distinguish antibodies to different viruses having genetic or antigenic similarities, due to what is known as serological ‘cross  reactivity’.

Serology tests for MERS CoV have not yet been validated in animals and may not be reliable. If these tests, which may not be sufficiently specific, are used in animals there is a risk that ‘false positive’ results will occur because it may not be possible to differentiate antibodies to MERS CoV from antibodies to other coronaviruses, commonly found in animals.

That is why tests in animals should focus on isolating and identifying the virus itself.

What would happen if MERS CoV is identified in animals?
If information from public health investigations identifies a possible animal source, OIE will support further joint investigations.

OIE Member Countries would be obliged to report a confirmed case of MERS CoV in animals to OIE, as an emerging disease’ in accordance with article 1.1.3 of the OIE Terrestrial Animal Health Code. If MERS CoV was identified in an animal this would not necessarily mean that the animal is a source of human infection. Detailed investigations would then be needed to understand the relationship between any animal cases and human cases, and whether a finding in animals would be significant for human infection.

What is OIE doing?
OIE is working closely with the WHO to support investigations into a possible animal source: an OIE expert participated in a WHO mission to the Kingdom of Saudi Arabia in June 2013 to investigate the source of MERS CoV. OIE also has a global informal network of experts on coronaviruses in animals who are closely monitoring the situation.

OIE develops and publishes international standards and guidelines on the prevention and control of animal diseases including zoonoses (animal diseases transmissible to humans). These science-based standards provide guidance on the best control measures which should be applied, where appropriate, to allow control of infection in the identified animal source.

The OIE is the reference organisation for international standards relating to animal health and zoonoses under the World Trade Organization Sanitary and Phytosanitary Agreement (SPS Agreement). Decisions related to safe trade in terrestrial animals and animal products must respect the standards, recommendations and guidelines found in the OIE Terrestrial Animal Health Code.

Although a relative to this virus had already been detected in bat species, and a fragment of viral genetic material matching the MERS CoV was recently found in one bat from Saudi Arabia, more evidence is needed to directly link the MERS CoV to bats or any other animal species.

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