In light of recent outbreaks of Middle East Respiratory Syndrome coronavirus (MERS-CoV), two studies provide new insights into this life-threatening pathogen, with the first identifying five different lineages of the virus that have circulated between humans and camels, and the second evaluating a MERS-CoV vaccine for camels that could work as a preemptive measure to reduce the pathogen's spread. Over the past three years, several MERS outbreaks have been reported in the Middle East and most recently in South Korea, with a fatality rate of roughly 35%. These outbreaks renew concerns about potential changes in the mode of transmission of this virus. Arabian camels are a common host for MERS-CoV, and one of the most likely sources of human infection; in these animals, the virus can diversify and then be passed to people, though little is known about how the MERS-CoV is evolving in this animal reservoir, or about its prevalence there and the route by which it is transmitted to humans. To gain more insights, Jamal Sabir et al. took samples from more than 1,300 camels in Saudi Arabia, the country most affected by MERS, between May 2014 and April 2015. The overall rate of MERS-CoV among this sample was 12%. Using genetic sequencing, the researchers identified five different lineages of MERS-CoVs, all of which contained human and camel MERS-CoV sequences, indicating that there is a low barrier for interspecies transmission. The wide range of CoVs and their aptitude for infecting multiple species suggests that more variations will emerge in the future. Although changes in human population density, climate conditions, and social factors may contribute to the spread of MERS-CoVs in other regions, such as the recent outbreak in South Korea, the prevention of transmission at the animal-human interface is likely to be the most efficient measure to contain the threat from this virus, the authors conclude.
In a second study, Bart Haagmans et al. tested the efficacy of a vaccine expressing the MERS-CoV spike protein in Arabian camels, using a modified poxvirus as the delivery method. After administering the vaccine both nasally and intramuscularly, all camels developed detectable levels of antibodies against MERS-CoV within three weeks. Upon infection with the virus, these MERS-CoV-vaccinated camels experienced only mild clinical symptoms and were found to have significantly lower levels of the virus compared to controls. The level of protection in MERS-Cov vaccinated camels correlated with levels of neutralizing antibodies they harbored. Since the vaccine uses a modified camelpox virus, vaccinated camels also experienced increased antibodies and protection against this pathogen, which commonly infects Arabian camels, as well.