A new study revealed MERS is particularly prevalent among young camels and has been around for at least two decades. The researchers noted, however, their findings do not prove that MERS spread to humans from camels, and more investigation into the origin of this respiratory illness is needed.
"Our findings suggest that continuous, longer-term surveillance will be necessary to determine the dynamics of virus circulation in dromedary camel populations," study senior author W. Ian Lipkin, of Columbia University in New York City, said in a news release from the American Society for Microbiology.
MERS, or Middle East respiratory syndrome, is a serious viral respiratory illness. The World Health Organization reports the illness has claimed 79 lives since 2012. Although most diagnosed cases of MERS occurred in Saudi Arabia, researchers were unsure about the source of this new virus.
Because the first known case of the illness involved a man who had four pet camels, researchers looking for the origin of MERS have focused on camels as well as bats.
In conducting the study, published Feb. 25 in mBio, the investigators collected blood samples from dromedary camels throughout Saudi Arabia. They also took swabs from the rectum and nose of camels as well as sheep and goats in November and December of 2013.
The scientists tested the samples looking for the active virus and antibodies reactive with the MERS virus. They also tested older blood samples taken from dromedary camels between 1992 and 2010.
The study revealed that 74 percent of the camels examined had MERS antibodies. Moreover, more than 80 percent of adult camels in Saudi Arabia had antibodies to the virus. The prevalence was even higher in younger camels. The researchers found 90 percent of those in the eastern part that were 2 years old or younger tested positive for MERS antibodies. Meanwhile 5 percent of young camels in the southwest also tested positive.
Active MERS virus was also identified in 35 percent of the young camels' nasal swabs and 15 percent of adult camels. The researchers noted MERS was found less often in rectal samples and not detected in blood. They concluded the virus is probably spread through respiratory secretions.
"Our study shows the MERS coronavirus is widespread," explained Lipkin. "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."
The researchers noted samples dating as far back as 1992 contained antibodies to the MERS virus, which suggests the MERS virus or a closely related virus has been infecting animals in Saudi Arabia for at least 20 years.
The U.S. Centers for Disease Control and Prevention has more about MERS.