The camel was owned by a Saudi man from Jeddah who recently contracted the disease. The animal tested positive using a polymerase chain reaction or PCR test, which looks for small bits of RNA from the virus in specimens such as mucous or saliva.
Dr. Ziad Memish, the Saudi deputy minister of health, said additional work is being done to chart the genetic sequence of the virus, which will then be compared to MERS viruses that have infected people.
If the finding is confirmed it will mark the first time the MERS coronavirus has been found in an animal.
Memish said in an email that the camel was tested as part of an investigation into a human case of MERS that was reported last week that involved a 43-year-old man from Jeddah who got sick in late October and who reportedly is in an intensive care unit in hospital.
"In this particular case there was a history of contact with sick animals that the patient owned," Memish said, adding that testing on other animals belonging to the man continues.
Bats have been identified as the likely ultimate source of the virus, though it's generally thought that another species is acting as a bridge to transmit the virus to people. That's because bat-human interactions are rare.
A study published in late August reported finding a segment of viral RNA in feces from an Egyptian tomb bat that was identical to the corresponding section of the MERS virus. But the fragment was so small other experts said was impossible to say if the full virus would have been identical as well.
As researchers around the world work to try to puzzle out the source of the MERS virus, attention focused on camels after several cases said they had contact with the beasts before becoming ill.
Also in August, European researchers reported finding antibodies that react to the MERS coronavirus in camels from Oman and the Canary Islands. A later study reported the same in camels from Egypt.
The discovery of antibodies means the camels had been previously infected with MERS or a MERS-like virus. But there is no way to tell when that infection took place. And without a sample of the virus that generated the antibodies, there is no way to know if it was MERS, or a related but different virus.
That's why the search has been on for animals that are currently infected. They are potential sources of viruses that can be isolated, sequenced and compared to the viruses that are causing illness in humans.
Marion Koopmans, a Dutch virologist who led the first study that found MERS antibodies in camels, said the Saudi finding is an interesting development. But she said it will be important to see the sequence of the virus the PCR test detected.
For one thing, there are other known camel coronaviruses, which at least in theory might have generated a positive hit on the MERS test.
"I would want to know for sure that the MERS corona(virus) PCR assay does not pick up those viruses," said Koopmans, chief of virology at the National Institute of Public Health for the Netherlands.
"PCR positive, that tells that there is most likely a coronavirus. But the sequencing will tell whether it is MERS corona. But it's of course a strong signal if they used the MERS coronavirus assays."
While finding the virus in an animal — particularly an animal that has contact with people — will be a coup, it won't solve all of MERS's mysteries.
Many MERS patients reported having no contact with animals before becoming sick. So where did those who didn't own camels contract the virus?
As well, finding the virus in an animal species does not automatically explain the route of transmission — how people become infected. Nor does it shed light on why the virus — which appears to have spread widely through camels in the Middle East and possibly North Africa — seems to have only recently turned its attention to humans?
"Let's assume that a very close virus is found in camels," Koopmans said.
"Then the question is: Given that so many animals test positive, then the most likely situation is that this is some kind of virus that has been circulating in camels for maybe a long time.... So what changed? What changed recently that explains that we now see these human cases?"Suggest a correction