The MERS coronavirus infected camels on a farm in Qatar linked to human cases but researchers can't tell whether the people were infected by the animals, which could be important in controlling outbreaks.
As of Dec. 2, 163 laboratory-confirmed cases of Middle East respiratory coronavirus or MERS, including 71 deaths, have been reported to the World Health Organization.
A journal editorial in Tuesday's issue of The Lancet Infectious Diseases notes there are reasons to be hopeful that targeting affected animals species and their handlers might eliminate MERS from the human population.
Nial Ferguson and Maria Van Kerkhove of Imperial College London in the UK said "an understanding of the role of animals in the transmission of [MERS coronavirus] is urgently needed to inform control efforts."
The pair were commenting on a study published in the same issue by researchers from The Netherlands, Qatar and the UK who said their genetic analysis of the samples from the same camels provides proof of the presence of MERS coronavirus in three dromedary camels in Qatar.
The virus sequences were similar but not identical to those found in two people on the farm.
"We cannot conclude whether the people on the farm were infected by the camels or vice versa, or if a third source was responsible," Dr. Mohammed Al Hajri of the Supreme Council of Health in Doha and his co-authors concluded.
People have spread MERS to each other, especially in health-care settings and households, but it's thought be a relatively inefficient source of transmission, a previous study suggests.
"There are reasons to be hopeful that animal-targeted controls might be effective," they said.
MERS has been reported but not confirmed in a camel in Saudi Arabia, and antibodies from MERS or a similar virus have also been found in camels in the Canary Islands, Oman, and Egypt.
A closely related virus has also been found in bats.
The commentary called the slow rate of growth of the epidemic in camels and humans a paradox but pointed to environmental contamination as one explanation of how the virus persists.
The research was funded by the European Union, the British charity Antigone and the Virgo consortium in the Netherlands.
Some of the authors have a pending patent for MERS coronavirus.