Concerns about Misinterpretation of Recent Scientific Data Implicating Dromedary Camels in Epidemiology of Middle East Respiratory Syndrome (MERS)

Samara, Emad M.; Abdoun, Khalid A.

Human-to-camel MERS-CoV transmission is also of importance. There is no doubt that everyone can question whether such form of transmission is actually happening in the case of MERS, but no one can deny it either. Ordinarily, all new pathogens are believed to emerge from animals (i.e., the source or reservoir) when ecological changes increase the pathogen's opportunities to enter the human population (i.e., the new host) and to generate subsequent human-to-human transmission. However, we might consider the reverse in the following scenario: a new host (i.e., DCs) acquires a new infectious agent (i.e., MERS-CoV) that emerges from an unknown source of infection (humans or any other source). Once infected, DCs will rapidly produce antibodies to MERS-CoV, and if the virus cannot induce a disease (i.e., MERS), DCs will have no clinical signs, viremia, or fatality cases. Now, if we assume that this infectious agent has an evolutionary rescue (e.g., genetic mutations) to enable its adaptation to the new environment, DCs will have an infectious agent with a set of genetic variants (genotypes) that differ from the original one. Therefore, we can clearly see that it is plausible to assume that humans (or any other source) are the ones who infected DCs in the first place. In fact, domestic cats, living in Hong Kong, were reported in 2003 to be infected with severe acute respiratory syndrome coronavirus (SARS-CoV) originating from humans (13) . Likewise, Memish (10) detected MERS-CoV sequences in a DC owned by an individual infected by MERS. Therefore, the presence of antibodies, viral nucleic acids, and quasispecies variants of MERS-CoV detected by the authors in their sampled DCs may suggest that dromedaries can be naturally infected with MERS-CoV from infected humans, although how this happens is yet unclear. Nonetheless, we should test archived human samples to demonstrate whether humans can be implicated or whether MERS-CoV truly emerges as a human pathogen prior to 2012 or not. In addition, we should entertain the idea that MERS-CoV in DCs (i.e., the new host) may adapt again and eventually lead to reemergence of the disease in human populations and subsequently to a massive epidemic attack, which, as we previously argued, is the key driver in the current debate.