SARS-CoV and MERS-CoV are two coronaviruses that received great attention due to their high pathogenicity and mortality rates in human populations. While SARS was controlled, MERS continues to be a global public health concern. To examine differences in the epidemic patterns of these two viruses, we collected all available sequences to compare the different evolutionary characteristics of SARS-CoV and MERS-CoV. Notably, almost all of the human infection cases occurred in the Middle East, and cases that occurred outside of the Middle East involved travelers from this region, while African infections have so far not been reported. It is not clear that genetic differences between Africans and Arabs lead to differences in susceptibility.
In this study, we compared their evolutionary dynamics to provide a One Health perspective of their different results of disease control. The phylogenetic network of SARS-CoVs showed that human isolates gathered into a “super-spreader” cluster, and were distinct from civet isolates. In contrast, dromedary camel- and human-isolated MERS-CoVs were clustered together. Thus, most clades of MERS-CoV can infect humans, and MERS-CoVs seem easier to spill over from animal-to-human interface. Although MERS-CoVs are endemic to dromedary camels in both the Middle East and Africa, all human infections are linked to the Middle East. The nucleotide sequences of the MERS-CoV receptor gene--dipeptidyl peptidase 4 (DPP4) from 30 Egyptians, 36 Sudanese, and 34 Saudi Arabians showed little difference.
Our study reveals the reason why MERS-CoV is not easily controlled. Analysis of genetic differences between Africans and Arabs suggest that human population differences in DPP4 might not be the reason for their different MERS prevalence, raising the possibility that other reasons, such as poorer disease surveillance in Africa, might explain these observations.