Identification of MERS-CoV in dromedary camels
Authors: Neil M Ferguson, Maria D Van Kerkhove
Journal: The Lancet Infectious Diseases (2013)

One health—an initiative designed to integrate human and veterinary health—received a boost in The Lancet Infectious Diseases. A multidisciplinary team of scientists from the Netherlands, Qatar, and the UK report the first definitive isolation of the Middle East respiratory syndrome coronavirus (MERS-CoV) in a non-human animal species, dromedary camels.1Haagmans BL Al Dhahiry SHS Reusken CBEM et al.Middle East respiratory syndrome coronavirus in dromedary camels: an outbreak investigation.Lancet Infect Dis. 2013; (published online Dec 17.)http://dx.doi.org/10.1016/S1473-3099(13)70690-XGoogle Scholar Phylogenetic analysis of the 4·2 kb partial viral sequence obtained from one animal show the virus to be almost identical to isolates obtained from two human cases who had had contact with the camels on the affected farm. The affected smallholding is part of a much larger farm complex located about 30 km northwest of Doha, Qatar, which has been the subject of intensive epidemiological investigation since the diagnosis of the first human case on the farm 2 months ago.2World Organisation for Animal Health (OIE)MERS-CoV, Qatar.http://www.oie.int/wahis_2/public/wahid.php/Reviewreport/Review?page_refer=MapFullEventReport&reportid=14454Google Scholar Although the virus has only been sequenced from one camel to date, some virological evidence of infection was reported in 11 of 14 camels on the farm, and serological evidence of exposure to a MERS-CoV-like virus was noted in all of them. The close phylogenetic similarity between virus isolated from people and animals strongly suggests cross-species transmission, but present data do not inform on the direction of that transmission. Notably, the camel and human virus sequences differ by two substitutions. As the investigators note, this divergence might be the end result of a chain of transmission in animals that introduced mutations. The original source of the detected human and camel infections is unknown, although the sequences closely match an isolate from a human case of MERS-CoV reported in Hafr Al-Batin, Saudi Arabia, in June, 2013. The detection of MERS-CoV in camels in Qatar is given greater weight by the reported, but as yet unconfirmed, detection of the virus in a camel in Saudi Arabia3Ministry of Health Portal Kingdom of Saudi ArabiaMOH: a new way discovered to recognize the source of novel coronavirus.http://www.moh.gov.sa/en/CoronaNew/PressReleases/Pages/mediastatemenet-2013-11-11-001.aspxGoogle Scholar and previous findings of antibodies to MERS-CoV, or a very similar virus, in camels in the Canary Islands, Oman,4Reusken CBEM Haagmans BL Müller MA et al.Middle East respiratory syndrome coronavirus neutralising serum antibodies in dromedary camels: a comparative serological study.Lancet Infect Dis. 2013; 13: 859-866Summary Full Text Full Text PDF PubMed Scopus (575) Google Scholar and Egypt.5Perera RA Wang P Gomaa MR et al.Seroepidemiology for MERS coronavirus using microneutralisation and pseudoparticle virus neutralisation assays reveal a high prevalence of antibody in dromedary camels in Egypt, June 2013.Euro Surveill. 2013; 18: 20574Crossref PubMed Scopus (269) Google Scholar A closely related but not identical virus has also been detected in bats.6Memish ZA Mishra N Olival KJ et al.Middle East respiratory syndrome coronavirus in bats, Saudi Arabia.Emerg Infect Dis. 2013; (published online November.)https://doi.org/10.3201/eid1911.131172Crossref PubMed Scopus (525) Google Scholar That MERS-CoV is a zoonosis is not surprising; assessment of the implications will nevertheless be challenging. A particular paradox is the slow rate of growth of the underlying epidemic, whether in camels, human beings, or other reservoir species. Environmental contamination is perhaps one mechanism that might explain the persistence of MERS-CoV in the absence of an explosive epidemic. This hypothesis was given recent support by a bioinformatics analysis suggesting that MERS-CoV virus has the hard outer and inner shell necessary for environmental persistence.7Goh GK Dunker AK Uversky V Prediction of intrinsic disorder in MERS-CoV/HCoV-EMC supports a high oral-fecal transmission.PLoS Curr. 2013; (published online Nov 13.)https://doi.org/10.1371/currents.outbreaks.22254b58675cdebc256dbe3c5aa6498bCrossref PubMed Scopus (59) Google Scholar An understanding of the role of animals in the transmission of MERS-CoV is urgently needed to inform control efforts. This virus can spread from person to person, sometimes causing substantial outbreaks,8Assiri A McGeer A Perl TM et al.Hospital outbreak of Middle East respiratory syndrome coronavirus.N Engl J Med. 2013; 369: 407-416Crossref PubMed Scopus (947) Google Scholar, 9Hijawi B Abdallat M Sayaydeh A et al.Novel coronavirus infections in Jordan, April 2012: epidemiological findings from a retrospective investigation.East Mediterr Health J. 2013; 19: S12-S18PubMed Google Scholar but whether the virus is capable of self-sustained (ie, epidemic) human-to-human transmission is unknown.10Cauchemez S Fraser C Van Kerkhove MD et al.Middle East respiratory syndrome coronavirus: quantification of the extent of the epidemic, surveillance biases, and transmissibility.Lancet Infect Dis. 2014; 14: 50-56Summary Full Text Full Text PDF PubMed Scopus (261) Google Scholar If self-sustained transmission in people is not yet underway, intensive control and risk-reduction measures targeting affected animal species and their handlers might eliminate the virus from the human population. Conversely, if zoonotic exposure causes only a small fraction of human infections, then even intensive veterinary control efforts would have little effect on cases in people. The figure shows these scenarios and highlights that low case detection rates do not allow the scenarios to be distinguished from the data now available. About one in five human cases have reported exposure to animals;11The WHO MERS-CoV Research GroupState of knowledge and data gaps of Middle East respiratory syndrome coronavirus (MERS-CoV) in humans.PLoS Curr. 2013; (published online Nov 12.)https://doi.org/10.1371/currents.outbreaks.0bf719e352e7478f8ad85fa30127ddb8Crossref PubMed Google Scholar this might be an underestimate of true zoonotic exposure and growth in case incidence is slow, so there are reasons to be hopeful that animal-targeted controls might be effective. Qatar, supported by WHO and the Food and Agriculture Organization, has done an exemplary integrated outbreak investigation, with rapid collection of specimens from several animal species and the environment on the infected farm. But substantially more genetic and epidemiological data (eg, for timings of exposure events and symptom onsets) from both animal and human cases are needed to unravel the complex transmission dynamics of this virus. Passive and active surveillance in human beings and animals needs to be enhanced across the affected region, and livestock trading and movement patterns characterised and monitored. Prompt reporting of outbreaks within the frameworks provided by present human and animal health regulations is essential, but we would add the caveat that such reports need to be as comprehensive as possible to be useful. The handling of the outbreak reported here1Haagmans BL Al Dhahiry SHS Reusken CBEM et al.Middle East respiratory syndrome coronavirus in dromedary camels: an outbreak investigation.Lancet Infect Dis. 2013; (published online Dec 17.)http://dx.doi.org/10.1016/S1473-3099(13)70690-XGoogle Scholar is a model that we hope is more widely adopted in future. The Medical Research Council provided centre funding. The funder had no role in the writing of this Comment. Middle East respiratory syndrome coronavirus in dromedary camels: an outbreak investigationOur study provides virological confirmation of MERS-CoV in camels and suggests a recent outbreak affecting both human beings and camels. We cannot conclude whether the people on the farm were infected by the camels or vice versa, or if a third source was responsible. Full-Text PDF