In a startling revelation, researchers have found the deadly coronavirus - responsible for Middle East Respiratory Syndrome (MERS) - among camels.
MERS, a serious viral respiratory illness, has been identified in 182 people since 2012, according to the World Health Organisation (WHO). Nearly 79 people have died from the condition.
"Our study shows the MERS coronavirus (MERS-CoV) is widespread," said W. Ian Lipkin of Columbia University, New York.
Adult camels were more likely to have antibodies to the virus while juveniles were more likely to have active virus.
"This indicates that infection in camels typically occurs in early life, and that if people get the virus from camels the most likely source is young camels," he added.
While most infections have occurred in Saudi Arabia, the origin of disease in most cases has remained unknown.
More From This Section
Efforts to identify an animal source of infection have focused on bats and camels.
The first known case of MERS was in a Saudi Arabian man who had four pet camels.
In the study, investigators from the US and Saudi Arabia conducted a comprehensive survey of camels throughout Saudi Arabia.
They collected blood samples and rectal and nasal swabs from camels, sheep and goats in November and December of 2013.
Using mobile laboratory equipment, they tested blood samples for antibodies reactive with MERS-CoV, and the swabs and blood for active virus.
They also analysed archived blood samples from dromedary camels taken from 1992 through 2010.
Overall, 74 percent of camels sampled countrywide had antibodies to MERS-CoV. More than 80 percent of adult camels throughout the country had antibodies to the virus.
The researchers also found that active virus was frequently detected in nasal swabs in 35 percent of young camels and 15 percent of adult camels countrywide.
It was less frequently found in rectal swabs and not in blood, indicating that the virus most likely is spread by respiratory secretions, said the study published in mBio, the online journal of the American Society for Microbiology.