Missing information in animal surveillance of MERS-CoV
Authors: Hiroshi Nishiura, Keisuke Ejima, Kenji Mizumoto
Journal: The Lancet Infectious Diseases (2014)

Chantal Reusken and colleagues1Reusken 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 (572) Google Scholar have identified neutralising antibodies against Middle East respiratory syndrome coronavirus (MERS-CoV) in dromedary camels, suggesting the role of camels in harbouring the virus and infecting human beings. The study findings suggest that bats and camels jointly play an important part in the persistence and evolution of MERS-CoV, resulting in spillover to the human population.1Reusken 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 (572) Google Scholar, 2de Wit E Munster VJ MERS-CoV: the intermediate host identified?.Lancet Infect Dis. 2013; 13: 827-828Summary Full Text Full Text PDF PubMed Scopus (15) Google Scholar Theoretical epidemiologists refer to such combinations of animal hosts as the reservoir community.3Nishiura H Hoye B Klaassen M Bauer S Heesterbeek H How to find natural reservoir hosts from endemic prevalence in a multi-host population: a case study of influenza in waterfowl.Epidemics. 2009; 1: 118-128Crossref PubMed Scopus (34) Google Scholar To confirm that the two animal species constitute a reservoir community, two conditions should be objectively examined.3Nishiura H Hoye B Klaassen M Bauer S Heesterbeek H How to find natural reservoir hosts from endemic prevalence in a multi-host population: a case study of influenza in waterfowl.Epidemics. 2009; 1: 118-128Crossref PubMed Scopus (34) Google Scholar First, the combination of reservoir hosts should permit persistence of the virus in natural settings (eg, by frequently transmitting the virus to other hosts), which is the necessary condition. Second, in the absence of the reservoir community, transmission cannot be maintained (by definition), which is referred to as the sufficient condition.3Nishiura H Hoye B Klaassen M Bauer S Heesterbeek H How to find natural reservoir hosts from endemic prevalence in a multi-host population: a case study of influenza in waterfowl.Epidemics. 2009; 1: 118-128Crossref PubMed Scopus (34) Google Scholar, 4Funk S Nishiura H Heesterbeek H Edmunds WJ Checchi F Identifying transmission cycles at the human-animal interface: the role of animal reservoirs in maintaining Gambiense human African trypanosomiasis.PLoS Comput Biol. 2013; 9: e1002855Crossref PubMed Scopus (86) Google Scholar If other animal hosts can also maintain transmission, the reservoir community will have to include these hosts. In view of these conditions, although the identification of antibodies in camels is remarkable, an explicit assessment of the epidemiological role of camels has yet to be made to elucidate the mechanism of emergence in human beings. How can a complete view of reservoir dynamics be achieved? The series of transmission in a population could be traced with serological techniques. Rather than doing a cross-sectional survey (to take a snapshot of prevalence), the identification of the reservoir host requires understanding of the incidence (ie, rate of new infections) to measure transmissibility. Serial cross-sectional surveys or large-scale follow-up of cohorts (of susceptible camels, not of those already infected) would be required. Alternatively, implementation of a transmission experiment with uninfected camels could also be useful, because the transmissibility of infected camels can be objectively quantified. Even a simple one-to-one transmission experiment could inform about the presence of substantial transmissibility.5Nishiura H Yen HL Cowling BJ Sample size considerations for one-to-one animal transmission studies of the influenza A viruses.PLoS One. 2013; 8: e55358Crossref PubMed Scopus (32) Google Scholar Of course, identification of the route of transmission from camels to human beings would also be of utmost importance, and could directly lead to prevention. In addition to such preventive effort, clarification of reservoir dynamics should be given a high priority, because identification of the major route of animal-to-human transmission, without an understanding of the overall picture of persistence and evolution in different hosts, is difficult. We declare that we have no conflicts of interest. Middle East respiratory syndrome coronavirus neutralising serum antibodies in dromedary camels: a comparative serological studyMERS-CoV or a related virus has infected camel populations. Both titres and seroprevalences in sera from different locations in Oman suggest widespread infection. Full-Text PDF