The majority of camels in Saudi Arabia have been infected with Middle East Respiratory Syndrome (MERS) virus, and the virus has been circulating among the animals there for at least 20 years, a new study suggests.
Researchers tested blood, nasal and rectal samples from dromedary (one hump) camels throughout Saudi Arabia, as well as archived blood samples from camels in the region that were collected as far back as 1992. MERS first appeared in people in September 2012, and since then, 182 people have been infected, most in Saudi Arabia. Seventy-nine people have died from the infection.
The first person known to have MERS was a Saudi Arabian man who owned four pet camels.
The new research found that 74 percent of camels had antibodies against the MERS virus, indicating that they had been infected with MERS virus or a very similar virus in the past. Antibodies were more common in adult camels than young camels: 95 percent of camels older than age 2 had antibodies against the virus, compared to 55 percent of camels younger than 2. [6 Superbugs to Watch Out For]
In contrast, younger camels were more likely to have active virus (35 percent of young camels had active virus in their nasal samples, compared to 15 percent of adult camels).
These finding suggest that, for camels, MERS infection "typically occurs in early life, and that if people get the virus from camels, the most likely source is young camels," study researcher Dr. W. Ian Lipkin of Columbia University, New York, said in a statement.
The archived blood samples also contained MERS antibodies, suggesting the MERS or a similar virus has been circulating in camels for at least two decades.
Previously, the researchers found that camels had antibodies against the MERS virus, and that some were infected with active virus. The new study is the first to perform a countrywide survey of camels in Saudi Arabia.
However, the new study does not prove that humans caught the virus from camels, and more studies are needed to rule out other possibilities. For example, it could be that another animal infects both humans and camels. The MERS virus has also been found in bats.
The active virus was more commonly found in nasal samples than in blood or rectal samples, indicating that it likely spreads through the air and respiratory secretions, the researchers said.
The study is published today (Feb. 25) in the journal mBio.