Coronavirus – Credit CDC PHIL
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As researchers discover and publish more information on the origins and reservoir hosts of the MERS coronavirus it is important that agencies and organizations like the World Health Organization and the OIE update their FAQs (Frequently Asked Questions) and information sheets.
The last OIE update was published in November (see OIE: Updated Q&A On MERS Coronavirus), and since then we've seen a number of new MERS studies, particularly involving camels (see EID Journal: MERS-Like Antibodies In Camels, UAE 2003-2013, The Lancet: Identification Of MERS Virus In Camels, Eurosurveillance: Seroprevalence Of MERS-like Antibodies In Middle Eastern Camels), and so it is appropriate that a new version be posted.
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My thanks to Lisa Schnirring for tweeting this first updated Q&A on the MERS virus for the new year from the OIE, the World Organization For Animal Health. I've only included excerpts, follow the link to read it in its entirety.
Update January 2014 - 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 released 31st December 2013, a total of 176 laboratory-confirmed cases in humans have been reported since September 2012, including 74 deaths.
What are coronaviruses?<SNIP>
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.
According to available information, most human cases of MERS do not report contact with animals.
Can animals become infected with MERS CoV?
Analyses carried out in November 2013 by a laboratory in the Netherlands seem to provide compelling evidence that MERS CoV has been isolated from 3 camels on a farm in Qatar, also linked to two human cases of MERS CoV. In this event, the exposure source of the humans and the camels (and possibly other animals) is not known i.e. the direction of transmission between the two species is not known and it is also not known whether the animals and humans were exposed to some other source of infection. Further investigations are needed to assess the implications of these findings.
Are animals responsible for MERS CoV infections in people?
More investigations are needed to assess the presence of MERS CoV in animal population and determine potential sources and modes of transmission. However a large survey could be difficult to conduct, because validated diagnostic tests are not widely available, and animals may only shed the virus for relatively short periods of time. Additional joint human health and animal 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 other animal species.
What about the suspicion that camelidae and other animals play a role in MERS?
Although recent results from a laboratory in the Netherlands seem to provide evidence that 3 camels were infected with MERS CoV, further investigations are needed to understand the significance of these findings and to assess the potential role of camels and possibly other animals in MERS. Subsequently, samples taken from this same herd and tested using the same technique are negative. Important surveillance for MERS-CoV in animals is being implemented to better understand the epidemiology, and the same herd is under systematic retesting.
It is important to remain open minded about all potential sources of exposure for human and animal cases until more information is available.
What about serological tests, or detection and virus isolation 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 species or strains of 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 confirmatory tests in animals should focus on isolating and identifying the virus itself.
For that purpose, it is possible to use techniques to amplify genomic sequences with polymerase chain reaction (RT-PCR), confirmed by sequencing the amplicons, or to isolate the virus itself following viral culture. Because of genetic similarities with other strains, to confirm the presence of MERS-CoV, the analyses have to identify the species concerned (MERS-CoV), not only the genus (betacoronavirus). To date, because of the novelty of this virus strain, the use of the human PCR test might reveal false positive results resulting from close strains circulating in animals. The complete sequencing of the genome or virus isolation thus remains the most reliable way to confirm the presence of MERS CoV.
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 to the OIE a confirmed case of MERS CoV in animals, 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.
