A new analysis of genetic history confirms the long-held suspicion that Middle East respiratory syndrome virus, which alarmed global health leaders in 2012 when it spilled over from camels to cause an often fatal illness in people, does not spread easily between humans.
At least not yet.
In a paper published today in the journal eLife, Fred Hutchinson Cancer Research Center’s Drs. Gytis Dudas and Trevor Bedford modeled phylogenetic trees, or genetic histories, of all available MERS genome sequences — 100 from camels and 174 from humans.
“The genomic data confirms that the MERS virus is not at the moment spreading readily from person to person,” said Bedford, an evolutionary biologist and the paper’s senior author. “Almost all of the cases in the Arabian Peninsula are short chains that spill over from camels, infect a few people and then die out. That had been suspected, but not quantified.”
The new analysis compared evolutionary changes in the camel and human genetic sequences to show that the virus jumped from camels to humans hundreds of times since 2012, with the 2,000-plus human cases recorded since resulting mostly from repeated spillovers rather than person-to-person spread.
“Andrew [co-author Andrew Rambaut, a professor at the University of Edinburgh’s Institute of Evolutionary Biology] had championed this idea for some time, and it had been accepted by most that it was not one introduction from camels into humans back in 2012,” Bedford said. “Our analysis placed it at somewhere between 300 and 800 introductions with each introduction being responsible for an average of three or four cases.”