While scientists are still trying to isolate the full virus from samples taken from the camels, the multiple fragments of RNA recovered are conclusive that the virus is MERS, Marion Koopmans, a Dutch virologist who is leading the laboratory work on the investigation, said in an interview.
"We have definitive proof that it's MERS coronavirus," Koopmans said in an interview from the Netherlands on Thursday.
The viral fragments were isolated from nose swabs taken from the camels, Koopmans said.
But finding infected camels and infected people on the same farm does not prove that the former transmitted the virus to the latter, she said.
It is theoretically possible that the camels contracted the virus from the people — two men, both of whom survived their brush with MERS. Or some other animal or animals on the farm may have played a role in the transmission dynamic.
"How they (the camels) got it and what the relationship (to humans) is, that still remains open, I think," said Koopmans, who is chief of virology for the National Institute of Public Health for the Netherlands.
She praised the Qatari investigators, saying the work done on the farm was thorough and carefully done, with lots of information and specimens gathered. Scientists in the Netherlands — who were asked to help — are still testing samples from other animals, and sifting through the information the Qataris gathered. There are only a few laboratories in the world that are equipped to do this type of work.
Koopmans cautioned against jumping to conclusions at this point.
"We have to put everything together carefully and then see what it tells us," she said. "It's still very much an ongoing investigation, so I think we need to really piece the information together."
To date the World Health Organization has confirmed 160 infections with the new virus, which is from the same family as the SARS coronavirus. All of the infections either occurred in, or have links back to six countries in the Middle East: Jordan, Saudi Arabia, Qatar, the United Arab Emirates, Oman and Kuwait.
In the 14 months since the world learned there was a new coronavirus spreading on the Arabian Peninsula, suspicion has often focused on camels. That's because from time to time there have been reports that an infected person owned camels or attended camel races. But the WHO says many of the people who have contracted this virus reported no contact with the beasts.
The working hypothesis is the virus originated in bats, as SARS likely did before it. But people typically don't have a lot of contact with bats, and scientists have assumed some animal or animals is playing a bridging role, transmitting MERS to people.
Koopmans and colleagues uncovered a big clue earlier this year, finding antibodies to MERS or a similar virus in camels from Oman and the Canary Islands. A later study found them in camels in Egypt as well.
But antibodies signal prior exposure to a pathogen. To confirm that camels play a role in this story, science needs evidence of current infection — which is what the Qatar team is reporting.
Earlier this month the deputy minister of health for Saudi Arabia, Dr. Ziad Memish, also reported a similar finding from a single camel in that country. Memish said at the time that work was underway to compare the genetic sequences of viral material taken from the camel and the man who owned him, who had also contracted the virus.
Memish has not responded to repeated requests for information on how that work is progressing.
Koopmans said the findings will answer some questions but raises others.
"This is our first clue which further fills out the whole story," agreed Bart Haagmans, a Dutch virologist who is involved in the laboratory side of this investigation.
"But there's more work to do, especially on routes of transmission."
Haagmans, who is with Erasmus Medical Centre in Rotterdam, said the team believes the findings are solid. They used three different tests, and found multiple fragments of viral RNA. As well, he said, the camels have developed antibodies to MERS.
What remains to be discovered — the key question the WHO would like to see answered — is how people are becoming infected with this virus. It is also critical to find out how much of a role animal-to-person spread is playing at this point and how much transmission is person to person.
"For sure there is a part of the outbreak that is caused by human-to-human transmission," Haagmans said.
"The question is, what is the fraction of these cases? And how many independent introductions do you have through zoonotic (from an animal) transmission?"