Science

Camels transmitted MERS to humans, but virus probably came from bats

One of the MERS virus' earliest victims was tending to sick camels
Viral genetic sequencing showed that one sick camel was the source of the man's infection
Camels may just be the MERS virus' latest safe harbor: evidence suggest it came from bats

One of the earliest known victims of the Middle East Respiratory Syndrome (MERS) coronavirus — a retired Saudi military man who owned a herd of camels outside of Jeddah — almost certainly was infected when he applied a topical medication to the runny nose of one of his sick animals, a new study says.

But the authors of the latest effort to pinpoint the origins of the MERS virus said that the farmer's camel was probably an intermediate MERS host, and suggested that bats named for the Egyptian tombs they inhabit may have been the virus' first sanctuary.

In a "brief report" published Online First by the New England Journal of Medicine, a team of Saudi biomedical researchers used a combination of old-fashioned field investigation and viral genetic sequencing to track down one of the MERS virus' earliest leaps from animal to human. Their inquiries showed that the Saudi victim, who died 15 days after being admitted to a hospital in Jeddah with severe shortness of breath, had tended to several camels who were suffering from an unusual nasal discharge.

One of those camels, the researchers found, carried a virus genetically identical to that found in the blood and nasal passages of the Saudi patient who died. The scientists found evidence that the man's nine camels had transmitted the virus among themselves in the period before the man was infected, since all carried antibodies, and had recovered from any ill effects.

The scientists cited evidence that the MERS virus did not transmit readily from camel to human or from human to human — at least in November 2013. Three of the patient's friends report having visited the camels daily with the victim, and were uninfected. The victim's 18-year-old daughter developed cold symptoms shortly after he was hospitalized, but was also found to have been uninfected.

But a sample of the MERS virus' genetic sequences suggest that the dromedary camels, who were made mildly ill when exposed, may have been the virus' intermediary host. They cited several studies published earlier suggesting that bats native to several Middle Eastern countries harbor a closely related virus. One 2013 study discovered that a small fragment of the human MERS virus's genetic sequence was identical to that found in an Egyptian tomb bat caught in Saudi Arabia.

But, the authors wrote, the exact origins of MERS, which by late March had killed 86 and sickened at least 206 people worldwide, remains a mystery.

"The exact reservoir that maintains the virus in its ecological niche has yet to be identified," they wrote.

 

 


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